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1

Antimicrobial fabric adsorbed iodine produced by radiation-induced graft polymerization  

NASA Astrophysics Data System (ADS)

Antimicrobial fabric was synthesized by radiation-induced graft polymerization of N-vinyl pyrrolidone onto polyolefine nonwoven fabric and subsequent adsorption of iodine. In response of the huge request for the antimicrobial material applied to face masks for swine flu in 2009, operation procedure of continuous radiation-induced graft polymerization apparatus was improved. The improved grafting production per week increased 3.8 times compared to the production by former operation procedure. Shipped antimicrobial fabric had reached 130,000 m2 from June until December, 2009.

Aoki, Shoji; Fujiwara, Kunio; Sugo, Takanobu; Suzuki, Koichi

2013-03-01

2

Graft polymerization using radiation-induced peroxides and application to textile dyeing  

NASA Astrophysics Data System (ADS)

To improve the dyeing affinity of ultra high molecular weight polyethylene (UHMWPE) fiber, surface treatment by radiation-induced graft polymerization was performed. Methyl methacrylate (MMA), acrylic acid (AA) and styrene (St) were used as the monomers. The grafting yields as a function of storage time after irradiation were examined. Although the grafting yield of St after the sulfonation processing was quite low compared with those of MMA and AA, it was successfully dyed to a dark color with a cationic dye. Some acid dyes can dye the grafted fiber with AA. The acid dye is distributed to the amorphous domains of the AA grafted fiber. The dyeing concentration depended on the grafting yield, and the higher the grafting yield the darker the dye color.

Enomoto, Ichiro; Katsumura, Yosuke; Kudo, Hisaaki; Soeda, Shin

2011-02-01

3

Application of proton beams to radiation-induced graft polymerization for making amidoxime-type adsorbents  

NASA Astrophysics Data System (ADS)

MeV proton beams have been successfully applied as ionizing radiation to induce graft polymerization of acrylonitrile to prepare amidoxime-type adsorbents on polyethylene film substrates. Dependence of degree of grafting (DG) on the pre-irradiation proton energy, beam current and fluence has been examined with use of FTIR absorption measurements and RBS. The DG is observed to be proportional to the deposited energy, and saturate at a fluence of the order of 10 13 cm -2 which is more than one order of magnitude smaller than the saturation fluence for molecular hydrogen release from the substrate. It is shown that graft polymerization could be possible deep into a substrate with thickness of hundreds of ?m, indicating a possibility to control distribution of functional groups with a spatial variation of the order of a micron.

Kitamura, Akira; Hamamoto, Shimpei; Taniike, Akira; Ohtani, Yusuke; Kubota, Naoyoshi; Furuyama, Yuichi

2004-02-01

4

Molecular Design, Graft Polymerization and Performance Evaluation of Radiation Curable Flame Retardant Monomers Derived from Phosphorus-Nitrogen Systems  

NASA Astrophysics Data System (ADS)

The textile industry is constantly seeking new technologies to make its production more efficient, economical and environmentally friendly. An exciting new strategy to impart value-added functional finishes to textiles is the use of radiation, such as ultraviolet (UV) light, to drive the polymerization of monomers onto the surface of the substrates. These grafted polymeric layers provide the fiber or fabric with interesting new properties, such as antimicrobial behavior, water and oil repellency or flame retardancy. With the aid of a photoinitiator, UV curing can take place very rapidly and the process is waterless and uses less energy than traditional textile wet processing. With these thoughts in mind, this research explores the molecular design, synthesis, UV induced graft polymerization and performance evaluation of nine phosphorus-based flame retardant monomers for cellulosic cotton substrates. All monomers in this work were easily prepared using one-pot reactions procedures. With the assistance of Irgacure 819 photoinitiator, seven of the nine monomers were shown to simultaneously graft and polymerize onto the surface of cotton fabrics under UV radiation. JMPRTM Pro 10 software was used to explore the effect of variables, such as monomer concentration, photoinitiator concentration and UV exposure time, on the yield of the grafted polymeric layer. Burn testing of the treated fabrics in the vertical, 45° and horizontal orientations showed that all nine monomers were effective flame retardants that function via the condensed phase mechanism by encouraging the formation of nonflammable char. These burn test results were validated by thermogravimetric analysis, which demonstrated quantitatively that all nine monomers strongly promote the generation of a protective char. Finally, scanning electron microscopy was used to examine the surface morphology of the treated fabrics and visualize the grafted polymeric layer.

Edwards, Brian Tyndall

5

Complex-forming polymer prepared by electron beam radiation-induced graft polymerization  

NASA Astrophysics Data System (ADS)

In order to prepare a complex-forming polymer useful as a selective adsorbent, radiation-induced graft polymerization of acrylonitrile onto a fibrous tetrafluoroethylene ethylene copolymer has been studied by using preirradiation method. The resulting grafted fibers were treated with 3% hydroxylamine alcohol-water solution, followed by controlling in alkali solution. The adsorbents containing amidoxime are able to take up transition metal ions from neutral and weakly acidic solutions while not sorbing the ions of alkaline and alkaline earth metals to any significant extent. It was shown that by introducing a small amount of hydrophilic groups to the fiber, it was possible to increase the exchange rate between the external water and the internal water interacted with functional groups in polymer matrix and to induce the diffusion of hydrated metal ions. The efficiency for adsorption of transition metal ions was successfully improved either by adding small amount of hydrophilic part composed of poly(acrylic acid) or by restricting the distribution of amidoxime groups at the fiber surface. A high stability of this adsorbents to various treatments ( alkali treatment at 80° C, contact with seawater for 24 h at 30° C, etc.) was confirmed. It's applicability to the recovery of uranium from seawater is demonstrated by laboratory scale experiments.

Okamoto, Jiro; Sugo, Takanobu; Katakai, Akio; Omichi, Hideki

6

Characterization of N-isopropyl acrylamide/acrylic acid grafted polypropylene nonwoven fabric developed by radiation-induced graft polymerization  

NASA Astrophysics Data System (ADS)

Radiation-induced graft copolymerization of N-isopropylacrylamide (NIPAAm) and acrylic acid (AA) mixture was carried out on polypropylene nonwoven fabric to develop a thermosensitive material and has been found to affect the thermal and physical characteristics of fabric. The grafted fabrics with different monomer ratios were characterized by thermal gravimetric analysis (TGA), fourier transform infrared spectroscopy (FTIR), differential scanning calorimetry (DSC), X-ray diffraction (XRD), contact angle and atomic force microscopy (AFM). Results of FTIR clearly indicated that poly(acrylic acid) and poly(N-isopropyl acrylamide) were successfully grafted onto the membrane surface. TGA results showed that the thermal stability of PP fabric increased after grafting of NIPAAm/AA. The crystallinity values from DSC and XRD were found to decrease with increase in degree of grafting because of the addition of grafted chains within the noncrystalline region. The decrease in contact angles of the grafted fabric with an increase of the degree of grafting shows that PNIPAAm/PAA exists as the hydrophilic component. The increase in surface roughness after grafting was observed by AFM.

Kumari, Mamta; Gupta, Bhuvanesh; Ikram, Saiqa

2012-11-01

7

Graft copolymers of polyurethane with various vinyl monomers via radiation-induced miniemulsion polymerization: Influential factors to grafting efficiency and particle morphology  

NASA Astrophysics Data System (ADS)

Graft copolymers of polyurethane (PU) with various vinyl monomers were synthesized through a one-pot but two-step miniemulsion polymerization process. Firstly, the polycondensation of isophorone diisocyanate (IPDI) with hydroxyl-terminated polybutadiene (HTPB) had been performed in aqueous miniemulsion at 40 °C in order to obtain PU dispersions. Consecutively, an in-situ graft copolymerization of the vinyl monomers with the synthesized PU was initiated by ?-ray radiation at room temperature. The grafting efficiency of PU with vinyl monomer ( GPU/monomer) was calculated from 1H NMR spectra and the particle morphology of the final hybrid latex was observed by transmission electron microscopy (TEM). As there was no monomer transferring in miniemulsion system, homogenous hybrid particles would be synthesized provided that the monomer was miscible with PU, such as styrene. With the increase of the polarity of the monomer, the compatibility of PU with monomer decreased. GPU/monomer varied as GPU/styrene(37%)> GPU/butyl acrylate (BA)(21%)> GPU/methyl methacrylate (MMA)(12%). The proportion of homogeneous nucleation would increase as the hydrophilicity of the monomer increased. High temperature would destabilize the miniemulsion so as to result in a less grafting efficiency. Compared to the phase separation during the seeded emulsion polymerization, the miniemulsion polymerization method facilitated the preparation of homogeneous materials owing to its monomer droplet nucleation mechanism.

Wang, Hua; Wang, Mozhen; Ge, Xuewu

2009-02-01

8

Protein adsorption characteristics of porous and tentacle anion-exchange membrane prepared by radiation-induced graft polymerization  

NASA Astrophysics Data System (ADS)

A polymer chain containing a diethylamino group was grafted onto the pore surface of a porous hollow-fiber membrane by radiation-induced graft polymerization. Dependence of the protein binding capacity of the membrane on environmental parameters such as salt concentration, pH and temperature was investigated. Saturation capacity of protein bound onto the graft chain containing ion-exchange group was governed by the conformation of the graft chain and the intensity of ion-exchange interaction. The conformation of the graft chain was investigated based on the pore radius of the membrane estimated from the permeation flux of a buffer solution through the membrane. By sufficiently permeating a bovine serum albumin (BSA) solution within the concentration range of 0.2-10 mg-BSA/ml through the membrane, the BSA binding capacity was determined. With increasing salt concentration or pH of the protein buffer solution, the graft chain shrank and BSA binding capacity decreased. On the other hand, the BSA binding capacity slightly increased with increasing temperature, and the conformation of the graft chain was insensitive to temperature in the range from 278 to 303 K. The bound BSA could be quantitatively eluted by permeating a buffer solution containing 0.5 M NaCl, and no deterioration in the BSA binding capacity was observed during five cycles of adsorption, elution and conditioning.

Tsuneda, Satoshi; Saito, Kyoichi; Sugo, Takanobu; Makuuchi, Keizo

1995-08-01

9

Desalination by electrodialysis with the ion-exchange membrane prepared by radiation-induced graft polymerization  

NASA Astrophysics Data System (ADS)

Ion-exchange membranes modified with the triethylamine [-N(CH 2CH 3) 3] and phosphoric acid (-PO 3 H) groups were prepared by radiation-induced grafting of glycidyl methacrylate (GMA) onto the polyolefin nonwavon fabric (PNF) and subsequent chemical modification of poly(GMA) graft chains. The physical and chemical properties of the GMA-grafted PNF and the PNF modified with ion-exchange groups were investigated by SEM, XPS, TGA, and DSC. Furthermore, electrochemical properties such as specific electric resistance, transport number of K +, and desalination were examined. The grafting yield increased with increasing reaction time and reaction temperature. The maximum grafting yield was obtained with 40% (vol.%) monomer concentration in dioxane at 60°C. The content of the cation- and anion-exchange group increased with increasing grafting yield. Electrical resistance of the PNF modified with TEA and -PO 3 H group decreased, while the water uptake (%) increased with increasing ion-exchange group capacities. Transport number of the PNF modified with ion-exchange group were the range of ca. 0.82-0.92. The graft-type ion-exchange membranes prepared by radiation-induced graft copolymerization were successfully applied as separators for electrodialysis.

Choi, Seong-Ho; Han Jeong, Young; Jeong Ryoo, Jae; Lee, Kwang-Pill

2001-01-01

10

Cu(II) Adsorption of Activated Carbon Fibers Produced by Radiation-Induced Graft Polymerization  

Microsoft Academic Search

In this work, the adsorption behaviors of activated carbon fibers (ACFs) containing chelating functional groups were studied in heavy metal ion removal. The ACFs were modified by electron beam and glycidyl methacrylate (GMA, CH2—CCH3COOCH2CHOCH2) graft polymerization in order to induce chelating functional groups, such as iminodiacetate (IDA, NH(CH2COOH)2) groups on the ACF surfaces. Fourier transform-infrared spectrometry (FT-IR) and X-ray photoelectron

Soo-Jin Park; Young-Mi Kim; Jae-Sup Shin

2005-01-01

11

The role of hydroperoxides as a precursor in the radiation-induced graft polymerization of methyl methacrylate to ultra-high molecular weight polyethylene  

NASA Astrophysics Data System (ADS)

A graft polymerization of methyl methacrylate (MMA) to ultra-high molecular weight polyethylene (UHMWPE) with Co-60 ?-ray irradiation in air at room temperature has been carried out. The grafting yields were measured as a function of the storage time (elapsed time from the end of irradiation to the start of grafting), and it was found that the yields reach at the maximum values at around several days since the end of irradiation. In order to clarify the precursor of the graft polymerization, changes of the radical yields and the carbonyl groups were measured as a function of storage time with ESR and microscopic FT-IR, respectively. From the similarities between the depth profiles of the hydroperoxide formation and the grafting products, it was concluded that the hydroperoxides can be main precursors of the grafting of the radiation-induced polymerization of MMA to UHMWPE under the given conditions.

Enomoto, Ichiro; Katsumura, Yosuke; Kudo, Hisaaki; Sekiguchi, Masayuki

2010-06-01

12

Chemical reactive filter paper prepared by radiation-induced graft polymerization—I  

NASA Astrophysics Data System (ADS)

Chelating filter papers with chemically bonded amidoxime groups were synthesized by radiation-induced grafting of acrylonitrile onto filter paper (W3) followed by chemical treatment with hydroxylamine. The effect of grafting conditions such as absorbed dose, dose rate, monomer concentration and filter paper thickness on the grafting yield was studied. It was found that the degree of grafting increases with increasing absorbed dose and dose rate, and then tends to level off at high doses. The order of the dependence of the initial grafting rate on the dose is found to be of 0.33. An increasing monomer concentration was accompanied by a significant increase in grafting. At high monomer concentration the initial rate of grafting is fast followed by a slow rate. The rate of grafting is controlled by the filter paper thickness and the diffusion of monomer into the interior of the filter paper. Mechanical properties of the prepared filter paper were improved over the ungrafted paper. The amidoxime filter papers were examined for adsorption of uranium concentration ranging between 10-100 ppm.

Dessouki, A. M.; El-Tahawy, M.; El-Boohy, H.; El-Mongy, S. A.; Badawy, S. M.

1999-06-01

13

Thermosensitive membranes by radiation-induced graft polymerization of N-isopropyl acrylamide/acrylic acid on polypropylene nonwoven fabric  

NASA Astrophysics Data System (ADS)

Radiation-induced graft copolymerization of N-isopropylacrylamide (NIPAAm) and acrylic acid (AA) mixture was investigated on polypropylene nonwoven fabric to develop a thermosensitive material. The grafting was carried out using methanol, acetone and butanone as homopolymerization inhibitor in the reaction medium. Butanone was observed to give the maximum grafting. It was observed that the grafting is significantly influenced by the reaction conditions, such as radiation dose, monomer concentration, monomer ratio, solvent composition and reaction temperature. The degree of grafting increased as the AA and NIPAAm concentration in the reaction medium increased. The degree of grafting increased as the AA fraction in the NIPAAm/AA mixture increased. The temperature dependence of the grafting process is very much governed by the thermosensitive nature of the grafted chains right from the stage when initial grafting has taken place.

Ikram, Saiqa; Kumari, Mamta; Gupta, Bhuvanesh

2011-01-01

14

Radiation-induced graft polymerization of acrylamide: Reverse osmosis properties of polyethylene-g-poly(acrylamide) membrane  

NASA Astrophysics Data System (ADS)

A study has been made of some properties of the graft copolymer obtained by direct radiation grafting of acrylamide (AAm) onto low density polyethylene (LDPE) films. The swelling behaviour was investigated for the grafted and alkali-treated graft copolymer and it was found that this depends mainly on the amount of hydrophilic groups and also on the type of electrolytes (K- or Nasalts). salts). Some other properties of the graft copolymer films such as dimensional change wet and dry, electrical conductivity, and mechanical properties were studied. A trial has been made of such membrane for reverse osmosis desalination of saline water. The effect of operating time, degree of grafting, applied pressure and feed concentration on the water flux and salt rejection was determined.

Dessouki, Ahmed M.; Hegazy, El-Sayed A.; El-Assy, Nasef B.; El-Boohy, Hussein A.

15

Simultaneous radiation induced graft polymerization of N-vinyl-2-pyrrolidone onto polypropylene non-woven fabric for improvement of blood compatibility  

NASA Astrophysics Data System (ADS)

In this study, N-vinyl-2-pyrrolidone (NVP) was grafted onto polypropylene non-woven fabric (PPNWF) through a simultaneous irradiation induced graft polymerization technique. Effect of the parameters of graft polymerization, i.e., monomer concentration, absorbed dose and dose rate, on the degree of grafting (DG) was investigated. The graft polymerization of NVP was confirmed by attenuated total reflectance Fourier transform infrared spectroscopy (ATR-FTIR) and X-ray photoelectron spectroscopy (XPS). A contact angle goniometry was used to test water contact angle (WCA) of original PPNWF and modified samples. The in vitro blood compatibility, including hemolysis, protein adsorption, platelet adhesion and activated partial thromboplastin time (APTT) of tested specimens, was evaluated. The results demonstrated that the hemocompatibility of PPNWF was improved via graft polymerization of NVP.

Li, Rong; Wang, Hengdong; Wang, Wenfeng; Ye, Yin

2013-07-01

16

Electron-beam induced RAFT-graft polymerization of poly(acrylic acid) onto PVDF  

NASA Astrophysics Data System (ADS)

This paper explores for the first time the post-radiation-induced-graft polymerization on solid substrate using reversible addition-fragmentation transfer (RAFT) mechanism. Radiation-induced graft polymerization onto polymers is a potentially interesting technique to create easily new materials from highly resistant polymers, e.g. surface graft polymerization of acrylic acid (AA) onto poly(vinylidene difluoride) (PVDF) improves its surface properties without losing its excellent mechanical properties. As a consequence of the radical nature of the polymerization processes it is difficult to control molecular weight of grafted chains, and therefore design and standardize the properties of the final product. RAFT polymerization is a suitable method to obtain monodisperse polymers. The ability of the RAFT agents to control the polymer chain length could be an interesting approach to improve the grafted polymers obtained by post-radiation-induced-graft polymerization technique. In this way, graft polymerization of AA onto electron-beam irradiated ?-PVDF was performed using trithiocarbonic acid bis(1-phenylethyl) ester as a RAFT agent to control the radical polymerization. We studied several grafting parameters such as solvent, monomer concentration and grafting time in order to achieve a poly(acrylic acid) (PAA) layer onto PVDF surface. Acetic acid was found to be the best solvent for many reasons, as to drive graft polymerization mainly to the polymer surface, complete solubility and stability of all reactants. Hydrolysis of PAA chains was also studied in order to remove the trithiocarbonate functionality from the grafted polymer. A mild chemical condition was achieved in order to have thiol groups that were detected onto the modified PVDF by specific enzymatic reaction.

Grasselli, M.; Betz, N.

2005-07-01

17

Radiation co-polymerization and its application in biotechnology  

E-print Network

The main results and achievements that have been done for the full duration of CRP reported as follows: (1) Radiation preparation of co-polymers, interpenetrating polymer networks and their applications in separation technology. (2) Preirradiation grafting co-polymerization of NIPAAm and other monomers on cotton cellulose fabric, silicone rubber etc and the discussion on mechanism. (3) UV-induced grafting and modification of polymers by high LET radiation.

HaHongFei; Yi Min; Zhai Mao Lin

1996-01-01

18

Chemical Modification of Cellulose Nanofibrils by Graft Polymerization  

E-print Network

Chemical Modification of Cellulose Nanofibrils by Graft Polymerization Arie Mulyadi and Yulin Deng Funding for this project was provided by IPST Fellowship Cellulose Nanofibrils (CNF) Merits-association tendency by hydrogen bonds of cellulose on surface: Agglomeration Poor water resistance Poor

Das, Suman

19

New simulation method for grafted polymeric brushes  

NASA Astrophysics Data System (ADS)

We present the first Monte Carlo simulation method for determining the force between two surfaces due to the interaction of end-grafted polymers. The method is an elaboration of recently devised techniques for measuring the pressure by introducing hard or repulsive walls. The approach is applied to the usual self-avoiding-walk lattice model, as well as to the fluctuating bond model devised by Carmesin and Kremer. The latter is found to offer very significant computational advantages. Our results are in qualitative agreement with recent theoretical predictions.

Dickman, Ronald; Hong, Daniel C.

1991-09-01

20

Impact of solvent selection on graft polymerization of acrylamide onto starch  

Technology Transfer Automated Retrieval System (TEKTRAN)

The impact on polymer properties (Mn, monomer conversion, graft content, graft efficiency and anhydroglucose units between grafts) that result from changing the solvent for the graft polymerization of acrylamide onto starch from water to dimethylsulfoxide (DMSO) was evaluated. Reaction conditions we...

21

Radiation-hardened polymeric films  

DOEpatents

The radiation-induced conductivity of polymeric dielectrics with low electronic mobility is reduced by doping with electron donor or electron acceptor compounds at a level of 10/sup 15/ to 10/sup 21/ molecules of dopant/cm/sup 3/. Polyesters, polyolefins, perfluoropolyolefins, vinyl polymers, vinylidene polymers, polycarbonates, polysulfones and polyimides can benefit from such a treatment. Usable dopants include 2,4,7-trinitro-9-fluorenone, tetracyanethylene, 7,7,8,8-tetracyanoquinodimethane, m-dinitrobenzene, 2-isopropylcarbazole, and triphenylamine.

Arnold, C. Jr.; Hughes, R.C.; Kepler, R.G.; Kurtz, S.R.

1984-07-16

22

Radiation-hardened polymeric films  

DOEpatents

The radiation-induced conductivity of polymeric dielectrics with low electronic mobility is reduced by doping with electron donor or electron acceptor compounds at a level of 10.sup.15 to 10.sup.21 molecules of dopant/cm.sup.3. Polyesters, polyolefins, perfluoropolyolefins, vinyl polymers, vinylidene polymers, polycarbonates, polysulfones and polyimides can benefit from such a treatment. Usable dopants include 2,4,7-trinitro-9-fluorenone, tetracyanethylene, 7,7,8,8-tetracyanoquinodimethane, m-dinitrobenzene, 2-isopropylcarbazole, and triphenylamine.

Arnold, Jr., Charles (Albuquerque, NM); Hughes, Robert C. (Albuquerque, NM); Kepler, R. Glen (Albuquerque, NM); Kurtz, Steven R. (Albuquerque, NM)

1986-01-01

23

Preparation of amidoxime-fiber adsorbents by radiation-induced grafting  

NASA Astrophysics Data System (ADS)

The fibrous adsorbents containing amidoxime groups were synthesized by radiation-induced graft polymerization of acrylonitrile onto polypropylene fibers, followed by functionalization of cyano groups to amidoxime groups with hydroxylamine. The polypropylene-based fibrous adsorbents exhibited a high grafting rate. The adsorption tests proved the performance of these fibrous adsorbents as a promising material for uranium recovery from seawater.

Kabay, Nalan; Katakai, Akio; Sugo, Takanobu

1995-02-01

24

GRAFT POLYMERIZATION OF ACRYLONITRILE ONTO STARCH-COATED POLYETHYLENE FILM SURFACES  

Technology Transfer Automated Retrieval System (TEKTRAN)

When starch-coated polyethylene (PE) films were allowed to react with acrylonitrile in the presence of ceric ammonium nitrate initiator, graft polymerization occurred to produce starch-polyacrylonitrile (PAN) coatings that contained about 25% grafted PAN, by weight. The graft copolymer coatings adh...

25

Recovery of cadmium from waste of scallop processing with amidoxime adsorbent synthesized by graft-polymerization  

NASA Astrophysics Data System (ADS)

Fabric adsorbent having amidoxime function was synthesized by radiation-induced graft-polymerization. This adsorbent was applied to the removal of Cd from the scallop waste. The scallop waste was homogenized as a pre-treatment. The obtained top layer was used for the Cd absorption experiment at various pH conditions. At pH 6, the adsorbent showed the highest performance in Cd adsorption. The concentration factor was thousand for Cd. Preliminary column experiment was also carried out. The amidoxime adsorbent recovered 96.1% of Cd in the waste solution.

Shiraishi, Tomoyuki; Tamada, Masao; Saito, Kyouichi; Sugo, Takanobu

2003-01-01

26

Radiation grafting of methyl methacrylate monomer on natural rubber latex. [Gamma radiation  

SciTech Connect

A method of radiation grafting of methyl methacrylate (MMA) monomer on natural rubber (NR) latex has been studied. The irradiation dose in radiation emulsion polymerization of MMA monomer was lower compared to the irradiation dose for grafting of MMA monomer on NR latex, in order to obtain the same degree of conversion. This is due to the size of the rubber particles which are quite large and, hence, not sufficient to ensure an ideal emulsion polymerization. The irradiation dose for radiation grafting of MMA monomer on latex was around 300 krad to obtain a 75% degree of conversion. However, this irradiation dose was lower compared to the irradiation dose for bulk polymerization of MMA momomer, in order to obtain the same degree of conversion. This is due to the gel effect in the viscous media. Radiation grafting of MMA monomer on NR latex does not influence the pH of the latex, but influences the viscosity significantly. The viscosity of the NR latex increased with an increase in irradiation dose, due to the increase of the total solid content in the latex. The MMA monomer converted to P-MMA in NR latex was largely grafted on the NR, or at least insoluble in a solvent for P-MMA, such as acetone or toluene. The hardness of the pure gum vulcanizate increased with an increase in the degree of grafting or P-MMA content, but the other physical properties, such as tensile strength, modulus, elongation at break, and thermal stability, were not greatly influenced by the degree of grafting. 9 references, 3 figures, 5 tables.

Sundardi, F.; Kadariah, S.

1984-05-01

27

Radiation grafting on natural films  

NASA Astrophysics Data System (ADS)

Different methods of polymer grafting using gamma irradiation are reported in the present study for the preparation of newly functionalized biodegradable films, and some important properties related to their mechanical and barrier properties are described. Biodegradable films composed of zein and poly(vinyl alcohol) (PVA) were gamma-irradiated in presence of different ratios of acrylic acid (AAc) monomer for compatibilization purpose. Resulting grafted films (zein/PVA-g-AAc) had their puncture strength (PS=37-40 N mm-1) and puncture deformation (PD=6.5-9.8 mm) improved for 30% and 50% PVA in blend, with 5% AAc under 20 kGy. Methylcellulose (MC)-based films were irradiated in the presence of 2-hydroxyethyl methacrylate (HEMA) or silane, in order to determine the effect of monomer grafting on the mechanical properties of films. It was found that grafted films (MC-g-HEMA and MC-g-silane) using 35% monomer performed higher mechanical properties with PS values of 282-296 N mm-1 and PD of 5.0-5.5 mm under 10 kGy. Compatibilized polycaprolactone (PCL)/chitosan composites were developed via grafting silane in chitosan films. Resulting trilayer grafted composite film (PCL/chitosan-g-silane/PCL) presented superior tensile strength (TS=22 MPa) via possible improvement of interfacial adhesion (PCL/chitosan) when using 25% silane under 10 kGy. Finally, MC-based films containing crystalline nanocellulose (CNC) as a filling agent were prepared and irradiated in presence of trimethylolpropane trimethacrylate (TMPTMA) as a grafted plasticizer. Grafted films (MC-g-TMPTMA) presented superior mechanical properties with a TS of 47.9 MPa and a tensile modulus (TM) of 1792 MPa, possibly due to high yield formation of radicals to promote TMPTMA grafting during irradiation. The addition of CNC led to an additional improvement of the barrier properties, with a significant 25% reduction of water vapor permeability (WVP) of grafted films.

Lacroix, M.; Khan, R.; Senna, M.; Sharmin, N.; Salmieri, S.; Safrany, A.

2014-01-01

28

Thermal stability of grafted fibers. [Gamma radiation  

SciTech Connect

Presented the experimental results on the study of thermal stability of grafted fibers, i.e., polypropylene-, polyester-, and rayon-grafted fibers. These fibers were obtained by radiation grafting processes using hydrophylic monomers such as 1-vinyl 2-pyrolidone, acrylic acid, N-methylol acrylamide, and acrylonitrile. The thermal stability of the fibers was studied using a Shimadzu Thermal Analyzer DT-30. The thermal stability of the fibers, which can be indicated by the value of the activation energy for thermal degradation, was not improved by radiation grafting. The degree of improvement depends on the thermal stability of the monomers used for grafting. The thermal stability of a polypropylene fiber, either a grafted or an ungrafted one, was found to be inferior compared to the polyester of a rayon fiber, which may be due to the lack of C=O and C=C bonds in the polypropylene molecules. The thermal stability of a fiber grafted with acrylonitrile monomer was found to be better than that of an ungrafted one. However, no improvement was detected in the fibers grafted with 1-vinyl 2-pyrrolidone monomer, which may be due to the lower thermal stability of poly(1-vinyl-2-pyrrolidone), compared to the polypropylene or polyester fibers. 17 figures, 3 tables.

Sundardi, F.; Kadariah; Marlianti, I.

1983-10-01

29

Light-induced surface graft polymerizations initiated by an anthraquinone dye on cotton fibers.  

PubMed

Anthraquinone and its derivatives could serve as photo-sensitizers and generate radicals and reactive oxygen species in polymers under exposure of UVA or day light. Such a property was utilized in development of novel light-induced surface radical graft polymerizations on cotton fibers that were dyed with an anthraquinone derivative, 2-ethylanthraquinone. Several functional monomers were directly grafted onto the dyed cotton fibers upon UVA exposure. The chemical and morphological structures and thermal properties of the grafted fibers were confirmed and characterized by Fourier transform infrared spectrometer (FTIR), scanning electron microscope (SEM) and thermal gravimetric analysis (TGA). Reaction conditions including concentrations of the photosensitizer, the amount of monomers, as well as UVA irradiation time could influence grafting efficiencies. More interestingly, the surface graft polymerization did not significantly change the light active functions of the agent, evidenced by the light-active antimicrobial functions of the grafted fibers. PMID:25129730

Zhuo, Jingyuan; Sun, Gang

2014-11-01

30

Surface modification of ultra high molecular weight polyethylene fibers via the sequential photoinduced graft polymerization  

NASA Astrophysics Data System (ADS)

In this study, a sequential photoinduced graft polymerization process was proposed to improve the poor interfacial bonding property of ultra high molecular weight polyethylene (UHMWPE) fibers. The polymerization was initiated by dormant semipinacol (SP) groups and carried out in a thin liquid layer. Methacrylic acid (MAA) and acryl amide (AM) were grafted stepwise onto the surface of UHMWPE fibers. Attenuated total reflectance infrared spectroscopy (ATR-IR) and thermo gravimetric analysis (TGA) confirmed the grafting. The analysis result of pyrolysis-gas chromatography/mass spectrometry (Py-GC/MS) indicated the structure of grafted chains. Scanning electron microscopy (SEM) images and atomic force microscopy (AFM) images revealed the apparent morphology changing, and the grafted layers were observed. Interfacial shear stress (IFSS) test of the modified fibers showed an extensively improved interfacial bonding property. The active groups grafted onto the fibers would supply enough anchor points for the chemical bonding with various resins or further reactions.

Li, Zhi; Zhang, Wei; Wang, Xinwei; Mai, Yongyi; Zhang, Yumei

2011-06-01

31

Aliphatic polyester-grafted starch composites by in situ ring opening polymerization*  

E-print Network

Aliphatic polyester-grafted starch composites by in situ ring opening polymerization* Abstract cornponenls has been evidenced by SEM observations. Growth of the polyester chains on the starch granules has on the synthesis and characterization of aliphatic polyester- grafted Etarch (Scheme 1 ) by in s i f i i ROP of E

Narayan, Ramani

32

Grafting of Polymers from Carbon Fiber. Anionic Graft Polymerization of Vinyl Monomers Initiated by Metallized Aromatic Rings on Carbon Fiber  

Microsoft Academic Search

The anionic graft polymerization of vinyl monomers onto carbon fiber initiated by metallized carbon fiber was investigated. The metalation of polycondensed aromatic rings of the carbon fiber surface was achieved by the treatment of carbon fiber with n-butyl-lithium (BuLi) in N, N, N?, N? -tetramethylethylenediamine (TMEDA) or hexamethylphosphorous triamide (HMPT) at 0°C. The anionic polymerization of methyl methacrylate (MMA) and

Norio Tsubokawa; Hiroshi Hamada; Yasuo Sone

1990-01-01

33

Radical grafting from carbon fiber surface: graft polymerization of vinyl monomers initiated by azo groups introduced onto the surface  

Microsoft Academic Search

This paper describes the radical graft polymerizations of vinyl monomers from carbon fiber surface initiated by azo groups introduced onto the fiber surface. The carbon fiber used in this experiment was the polyacrylonitrile type. The introduction of azo groups onto the carbon fiber surface was achieved by the reaction of 4,4'-azobis (4-cyanopentanoic acid) with isocyanate groups which were previously attached

Kazuhiro Fujiki; Nobuo Motoji; Akira Yoshida

1995-01-01

34

Radiation sterilization of polymeric implant materials  

Microsoft Academic Search

High-energy irradiation sterilization of medical devices and implants composed of polymeric biomaterials that are in contact with tissue and\\/or blood, may adversely affect their long-term mechanical and\\/or biological performance (tissue and\\/or blood compatibility). Since many polymeric implants may contain trace quantities of catalysts and\\/or other additives, the effect of high-energy radiation on these additives, and possible synergistic effects with the

Stephen D. Bruck; Edward P. Mueller

1988-01-01

35

Radiation induced graft copolymerization of methyl methacrylate onto chrome-tanned pig skins  

NASA Astrophysics Data System (ADS)

Graft copolymerization of methyl methacrylate (MMA) onto chrome-tanned pig skins was carried out by the irradiation with 60Co ?-rays. The grafted polymethyl methacrylate (PMMA) chains were isolated by acid hydrolysis of the collagen backbone in order to characterize the graft copolymers. Proof of grafting was obtained through the detection of amino acid endgroups in the isolated grafts by reaction with ninhydrin. The grafting yield of MMA in aqueous emulsion was found to be higher than that for pure MMA and MMA in acetone. The degree of grafting increases with increasing monomer concentration in emulsion and reaches maximum at radiation dose ca 15 kGy. The yield of grafting is very high - ca 90% of monomer converts into copolymer and only 10% is converted into homopolymer. The present paper reports the physical properties of chrome-tanned pig skins after graft polymerization with MMA in emulsion. Modified leathers are more resistant against water absorption and abrasion in comparison with unmodified ones. They have more uniform structure over the whole surface, greater thickness and stiffness. The results reported seem to indicate that MMA may be used in the production of shoe upper and sole leathers. The mechanism of some of the processes occuring during radiation grafting of MMA in water emulsion on tanned leathers has been also suggested and discussed.

Pietrucha, K.; P?kala, W.; Kroh, J.

36

The synthesis of well-defined poly(vinylbenzyl chloride)-grafted nanoparticles via RAFT polymerization  

PubMed Central

Summary We describe the use of one of the most advanced radical polymerization techniques, the reversible addition fragmentation chain transfer (RAFT) process, to produce highly functional core–shell particles based on a silica core and a shell made of functional polymeric chains with very well controlled structure. The versatility of RAFT polymerization is illustrated by the control of the polymerization of vinylbenzyl chloride (VBC), a highly functional monomer, with the aim of designing silica core–poly(VBC) shell nanoparticles. Optimal conditions for the control of VBC polymerization by RAFT are first established, followed by the use of the “grafting from” method to yield polymeric brushes that form a well-defined shell surrounding the silica core. We obtain particles that are monodisperse in size, and we demonstrate that the exceptional control over their dimensions is achieved by careful tailoring the conditions of the radical polymerization. PMID:23843918

Moraes, John; Ohno, Kohji; Gody, Guillaume; Maschmeyer, Thomas

2013-01-01

37

Structure-property Relationships in Radiation Grafted Poly(tetrafluoroethylene)- graft -polystyrene Sulfonic Acid Membranes  

Microsoft Academic Search

Structure-property relationships in poly(tetrafluoroethylene)-graft-polystyrene sulfonic acid (PTFE-g-PSSA) membranes prepared by radiation-induced grafting of styrene onto poly(tetrafluoroethylene) (PTFE) films using simultaneous radiation-induced grafting followed by sulfonation reaction were established. The physico-chemical properties of the membranes such as ion exchange capacity, swelling and ionic conductivity were correlated with the degree of grafting and the structural changes taking place in the membrane matrix

Mohamed Mahmoud Nasef; Hamdani Saidi

2005-01-01

38

Comparison of surface modifications of poly(ether urethanes) by chemical infusion and graft polymerization  

SciTech Connect

Our approach to surface modification uses the chemical infusion process to introduce materials into the outermost layer of the polymeric material, thereby altering the surface without changing the bulk properties of the polymer. The infused materials may slowly diffuse out of the infusion layer if they are volatile or highly mobile. However, if polymeric infusant materials are employed, they may become chain entangled with the host polymer and result in a permanently modified surface. A second approach utilizes photo-initiated graft polymerization of poly(ether urethanes) with an appropriate monomer. We have explored both of these methods by examining the infusion of polyvinylpyrrolidone (PVP) and poly(ethylene glycol) (PEG) into commercially available poly(ether urethanes) and the graft polymerization of N-vinyl pyrrolidone onto poly(ether urethanes). Results are presented here. 7 refs., 1 tab.

Wrobleski, D.A.; Cash, D.L.; Hermes, R.E.

1988-01-01

39

Polymer-grafted lignin surfactants prepared via reversible addition-fragmentation chain-transfer polymerization.  

PubMed

Kraft lignin grafted with hydrophilic polymers has been prepared using reversible addition-fragmentation chain-transfer (RAFT) polymerization and investigated for use as a surfactant. In this preliminary study, polyacrylamide and poly(acrylic acid) were grafted from a lignin RAFT macroinitiator at average initiator site densities estimated to be 2 per particle and 17 per particle. The target degrees of polymerization were 50 and 100, but analysis of cleaved polyacrylamide was consistent with a higher average molecular weight, suggesting not all sites were able to participate in the polymerization. All materials were readily soluble in water, and dynamic light scattering data indicate polymer-grafted lignin coexisted in isolated and aggregated forms in aqueous media. The characteristic size was 15-20 nm at low concentrations, and aggregation appeared to be a stronger function of degree of polymerization than graft density. These species were surface active, reducing the surface tension to as low as 60 dyn/cm at 1 mg/mL, and a greater decrease was observed than for polymer-grafted silica nanoparticles, suggesting that the lignin core was also surface active. While these lignin surfactants were soluble in water, they were not soluble in hexanes. Thus, it was unexpected that water-in-oil emulsions formed in all surfactant compositions and solvent ratios tested, with average droplet sizes of 10-20 ?m. However, although polymer-grafted lignin has structural features similar to nanoparticles used in Pickering emulsions, its interfacial behavior was qualitatively different. While at air-water interfaces, the hydrophilic grafts promote effective reductions in surface tension, we hypothesize that the low grafting density in these lignin surfactants favors partitioning into the hexanes side of the oil-water interface because collapsed conformations of the polymer grafts improve interfacial coverage and reduce water-hexanes interactions. We propose that polymer-grafted lignin surfactants can be considered as random patchy nanoparticles with mixed hydrophilic and hydrophobic domains that result in unexpected interfacial behaviors. Further studies are necessary to clarify the molecular basis of these phenomena, but grafting of hydrophilic polymers from kraft lignin via radical polymerization could expand the use of this important biopolymer in a broad range of surfactant applications. PMID:25046477

Gupta, Chetali; Washburn, Newell R

2014-08-12

40

Inorganic Surface Nanostructuring by Atmospheric Pressure Plasma-Induced Graft Polymerization  

E-print Network

and Biomolecular Engineering, UniVersity of California, Los Angeles, Los Angeles, California 90095-1592 Recei by graft polymerization in both N-methyl-2-pyrrolidone (NMP) and in an NMP/water solvent mixture, and adsorbed surface water. The surface number density of active sites was critically dependent on the presence

Hicks, Robert F.

41

Modification of polymeric substrates using surface-grafted nanoscaffolds  

NASA Astrophysics Data System (ADS)

Surface grafting and modification of poly(acrylic acid) (PAA) were performed on nylon 6,6 carpet fibers to achieve permanent stain and soil resistance. PAA was grafted to nylon and modified with 1H, 1H-pentadecafluorooctyl amine (PDFOA) using an amidation agent, 4-(4,6-dimethoxy-1,3,5-triazin-2-yl)-4-methylmorpholinium chloride (DMTMM). The first goal was to optimize acrylamide modification of PAA in solution. Aqueous reactions with taurine, hydroxyethyl amine, and butyl amine progressed ˜100%, while PDFOA reactions in MeOH progressed ˜80%. Reaction products precipitated at 77% butyl or 52% PDFOA acrylamide contents. The second goal was to optimize the PAA grafting process. First, PAA was adsorbed onto nylon 6,6 films. Next, DMTMM initiated grafting of adsorbed PAA. PAA surface coverage was ˜78%, determined by contact angle analysis of the top 0.1--1 nm and x-ray photoelectron spectroscopy (XPS) analysis of the top 3--10 nm. The third goal was to modify PAA grafted nylon films with butyl amine and PDFOA. Randomly methylated beta-cyclodextrin (RAMEB) solubilized PDFOA in water. Contact angle detected ˜100% surface reaction for each amine, while XPS detected ˜77% butyl amine (H2O) and ˜50% for PDFOA (MeOH or H2O pH = 7) reactions. In H2O pH = 12, the PDFOA reaction progressed ˜89%, perhaps due to greater efficiency, access and solubility. The fourth goal was to perform surface depth profiling via angle-resolved XPS analysis (ARXPS). The PAA surface coverage from contact angle and XPS was confirmed. Further, adsorbed PAA was thicker than grafted PAA, supporting the theory that PAA adsorption occurs in thick layers onto nylon followed by DMTMM-activated spreading and grafting of thinner PAA layers across the surface. The PDFOA reaction in McOH produced a highly fluorinated but thin exterior and an unreacted PAA interior. The PDFOA reaction in H 2O pH = 12 produced a completely fluorinated exterior and highly fluorinated interior. Thus surface modification levels from contact angle and XPS were confirmed. The final goal was to PAA-graft and PDFOA-modify nylon 6,6 fabrics and carpets. PDFOA modification achieved significant water and oil repellency. Stainblocking was slightly improved for ionized PAA-g-nylon and greatly improved for PDFOA-modified PAA-g-nylon. However, traditional stainblockers may be necessary to completely prevent dye penetration into carpet tufts.

Thompson, Kimberlee Fay

42

Preparation of hollow-fiber membranes by plasma-graft filling polymerization for organic-liquid separation  

Microsoft Academic Search

Filling-type hollow-fiber membranes for separating organic-liquid mixtures were prepared by plasma-graft polymerization technique using porous hollow-fiber substrates. Methyl acrylate (MA) was used as the grafting monomer. From analyses with scanning electron microscope (SEM), optical microscope, XPS imaging and micro FT-IR, it was confirmed that grafted polymer filled the pores of the hollow-fiber substrates and the thickness of this grafted layer

Teruhiko Kai; Toshinori Tsuru; Shin-ichi Nakao; Shoji Kimura

2000-01-01

43

Immobilization of peroxidase on SPEU film via radiation grafting  

NASA Astrophysics Data System (ADS)

The acrylic acid or acrylamide were grafted via radiation onto segmented polyetherurethane (SPEU) film which is a kind of biocompatible material. Then the Horse radish peroxidase was immobilized on the grafted SPEU film through chemical binding. Some quantitative relationships between the percent graft and the activity, amount of immobilized enzyme were given. The properties and application of obtained biomaterial was studied as well.

Hongfei, Ha; Guanghui, Wang; Jilan, Wu

44

Membrane surface modification via polymer grafting and interfacial polymerization  

Technology Transfer Automated Retrieval System (TEKTRAN)

Membrane separation is an important technology for separating food ingredients and fractionating high-value substances from food processing by-products. Long-term uses of polymeric membranes in food protein processing are impeded by formation of fouled layers on the membrane surface. Surface modif...

45

The effects of early postoperative radiation on vascularized bone grafts  

SciTech Connect

The effects of early postoperative radiation were assessed in free nonvascularized and free vascularized rib grafts in the canine model. The mandibles of one-half of the dogs were exposed to a cobalt 60 radiation dose of 4080 cGy over a 4-week period, starting 2 weeks postoperatively. The patency of vascularized grafts was confirmed with bone scintigraphy. Histological studies, including ultraviolet microscopy with trifluorochrome labeling, and histomorphometric analyses were performed. Osteocytes persist within the cortex of the vascularized nonradiated grafts to a much greater extent than in nonvascularized, nonradiated grafts. Cortical osteocytes do not persist in either vascularized or nonvascularized grafts subjected to radiation. New bone formation is significantly retarded in radiated grafts compared with nonradiated grafts. Periosteum and endosteum remained viable in the radiated vascularized grafts, producing both bone union and increased bone turnover, neither of which were evident to any significant extent in nonvascularized grafts. Bone union was achieved in vascularized and non-vascularized nonradiated bone. In the radiated group of dogs, union was only seen in the vascularized bone grafts.

Evans, H.B.; Brown, S.; Hurst, L.N. (Division of Plastic and Reconstructive Surgery, University of Western Ontario, London (Canada))

1991-06-01

46

Application of radiation-graft material for metal adsorbent and crosslinked natural polymer for healthcare product  

NASA Astrophysics Data System (ADS)

Graft polymerization and crosslinking in radiation processing are attractive techniques for modification of the chemical and physical properties of conventional polymers. The graft polymerization and subsequent chemical treatment can introduce a chelate agent function into a conventional polymer such as polyethylene. The obtained amidoxime fibrous adsorbent was applied to the recovery of uranium from seawater. Soaking of 350 kg adsorbent 12 times in seawater led to the collection of 1 kg of uranium. Natural polymers such as derivatives of starch and cellulose were radiation-crosslinked to form hydrogels. Mats of crosslinked carboxylmethyl cellulose were evaluated by 68 patients after surgical operation. No bedsore was observed in almost of all patients after operation. This product was commercialized as "Non-bedsore" in Japan.

Tamada, Masao; Seko, Noriaki; Yoshii, Fumio

2004-09-01

47

Pre-irradiation induced emulsion co-graft polymerization of acrylonitrile and acrylic acid onto a polyethylene nonwoven fabric  

NASA Astrophysics Data System (ADS)

A pre-irradiation induced emulsion co-graft polymerization method was used to introduce acrylonitrile and acrylic acid onto a PE nonwoven fabric. The use of acrylic acid is meant to improve the hydrophilicity of the modified fabric. The kinetics of co-graft polymerization were studied. The existence of polyacrylonitrile (PAN) and poly(acrylic acid) (PAAc) graft chains was proven by Fourier transform infrared spectroscopy (FTIR) analysis. The existence of the nitrile groups in the graft chains indicates that they are ready for further amidoximation and adsorption of heavy metal ions.

Liu, Hanzhou; Yu, Ming; Ma, Hongjuan; Wang, Ziqiang; Li, Linfan; Li, Jingye

2014-01-01

48

A FTIR and SEM study of PS radiation grafted fluoropolymers: influence of the nature of the ionizing radiation on the film structure  

Microsoft Academic Search

This study deals with the structure of polymeric films obtained by radiation grafting of polystyrene (PS) in poly(vinylidene fluoride) (PVDF) and poly(vinylidene fluoride\\/hexafluoropropylene) P(VDF\\/HFP). These fluoropolymers differ by the small HFP amount present in the copolymer, which plasticizes PVDF and favors the chain mobility. Peroxide grafting kinetic results obtained according to different parameters such as the irradiation type (swift heavy

C. Aymes-Chodur; N. Betz; M.-C. Porte-Durrieu; C. Baquey; A. Le Moël

1999-01-01

49

Towards multifunctional surfaces using the plasma-induced graft-polymerization (PIGP) process: Flame and waterproof cotton textiles  

Microsoft Academic Search

In order to produce multifunctional surfaces, water-repellent treatment combined with fire retardant finishes on cotton fabrics have been investigated by using the cold plasma technique. Three different protocols involving Ar plasma-induced graft-polymerization (PIGP) of flame retardant monomers (acrylate phosphate and phosphonates derivatives) combined to a water-repellent treatment – CF4 plasma treatment or Ar plasma induced graft polymerization of 1,1,2,2, tetrahydroperfluorodecylacrylate

M. J. Tsafack; J. Levalois-Grützmacher

2007-01-01

50

Enhanced microwave absorption performance of polyaniline-coated CNT hybrids by plasma-induced graft polymerization  

NASA Astrophysics Data System (ADS)

Highly conducting CNT/polyaniline hybrids were prepared by plasma-induced graft polymerization, i.e., plasma pretreatment of CNTs and further in situ polymerization of aniline. Plasma pretreatment made more aniline grafted on the CNTs' surface by the role of oxygen radicals. SEM images showed that the surfaces of CNTs were uniformly coated by PANI. FTIR showed that there was presence of strong interaction between CNTs and PANI molecular chains. The conductivity of CNT/PANI hybrids with plasma treatment is higher than that of CNT/PANI hybrids without plasma pretreatment (0.443 S/cm at 0 W) or pretreated by acid oxidation method. Importantly, the microwave absorption properties were investigated by measuring complex permeability, complex permittivity and reflection loss in a frequency of 2-18 GHz. The microwave absorption enhancement of CNT/PANI hybrids results mainly from dielectric loss rather than magnetic loss due to higher value of dielectric loss.

Cheng, Junye; Zhao, Bin; Zheng, Shiyou; Yang, Junhe; Zhang, Deqing; Cao, Maosheng

2015-01-01

51

Plasma polymerized thin coating as a protective layer of carbon nanotubes grafted on carbon fibers  

NASA Astrophysics Data System (ADS)

Nanoparticles addition is widely studied to improve properties of carbon fiber reinforced composites. Here, hybrid carbon fiber results from grafting of carbon nanotubes (CNT) by Chemical Vapor Deposition (CVD) on the carbon fiber for mechanical reinforcement and conductive properties. Both tows and woven fabrics made of the hybrid fibers are added to the matrix for composite processing. However handling hybrid fibers may induce unwilling health risk due to eventual CNT release and a protective layer is required. A thin coating layer is deposited homogeneously by low pressure plasma polymerization of an organic monomer without modifying the morphology and the organization of grafted CNTs. The polymeric layer effect on the electrical behavior of hybrid fiber is assessed by conductivity measurements. Its influence on the mechanical properties is also studied regarding the interface adhesion between fiber and matrix. The protective role of layer is demonstrated by means of friction constraints applied to the hybrid fiber.

Einig, A.; Rumeau, P.; Desrousseaux, S.; Magga, Y.; Bai, J. B.

2013-04-01

52

Enhanced microwave absorption performance of polyaniline-coated CNT hybrids by plasma-induced graft polymerization  

NASA Astrophysics Data System (ADS)

Highly conducting CNT/polyaniline hybrids were prepared by plasma-induced graft polymerization, i.e., plasma pretreatment of CNTs and further in situ polymerization of aniline. Plasma pretreatment made more aniline grafted on the CNTs' surface by the role of oxygen radicals. SEM images showed that the surfaces of CNTs were uniformly coated by PANI. FTIR showed that there was presence of strong interaction between CNTs and PANI molecular chains. The conductivity of CNT/PANI hybrids with plasma treatment is higher than that of CNT/PANI hybrids without plasma pretreatment (0.443 S/cm at 0 W) or pretreated by acid oxidation method. Importantly, the microwave absorption properties were investigated by measuring complex permeability, complex permittivity and reflection loss in a frequency of 2-18 GHz. The microwave absorption enhancement of CNT/PANI hybrids results mainly from dielectric loss rather than magnetic loss due to higher value of dielectric loss.

Cheng, Junye; Zhao, Bin; Zheng, Shiyou; Yang, Junhe; Zhang, Deqing; Cao, Maosheng

2015-04-01

53

Radiation-induced grafting of acrylic acid onto polyethylene filaments  

NASA Astrophysics Data System (ADS)

Radiation-induced grafting of acrylic acid onto high density polyethylene (PE) filaments was carried out in order to raise softening temperature and impart flame retardance and hydrophilic properties. Mutual ?-irradiation method was employed for the grafting in a mixture of acrylic acid (AA), ethylene dichloride and water containing a small amount of ferrous ammonium sulfate. The rate of grafting was very low at room temperature. On the other hand, large percent grafts were obtained when the grafting was performed at an elevated temperature. Activation energy for the initial rate of grafting was found to be 17 {kcal}/{mol} between 20 and 60°C and 10 {kcal}/{mol} between 60 and 80°C. Original PE filament begins to shrink at 70°C, show maximum shrinkage of 50% at 130°C and then breaks off at 136°C. When a 34% AA graft is converted to metallic salt such as sodium and calcium, the graft filament retains its filament form even above 300°C and gives maximum shrinkage of 15%. Burning tests by a wire-netting basket method indicate that graft filaments and its metallic salts do not form melting drops upon burning and are self-extinguishing. Original PE filament shows no moisture absorption, however, that of AA-grafted PE increases with increasing graft percent. The sodium salt of 15% graft shows the same level of moisture regain as cotton. The AA-grafted PE filament and its metallic salts can be dyed with cationic dyes even at 1% graft. Tensile properties of PE filament is impaired neither by grafting nor by conversion to metallic salts.

Kaji, K.; Okada, T.; Sakurada, I.

54

Utilizing advanced polymerization techniques for simplifying polymer grafting from silica colloidal crystal substrates  

NASA Astrophysics Data System (ADS)

Polyacrylamide has been well established as a biocompatible material when Polyacrylamide gel electrophoresis (PAGE) came into existence in the 1960s. Under aqueous buffer conditions it becomes non-adsorptive to proteins and due to its molecular level pore forming nature could be used in size based biomolecule separations. Since then considerable research has been done to explore the non-adsorptive nature of polyacrylamide on a platform or substrate. Attempts were made to grow polyacrylamide chains from silica as a substrate which can then be used in various protein separation techniques. Based on an ionic polymerization method which was used for gel casting in PAGE, polymers were grown on silica gel. Though considerable thickness could be achieved, polymerization was not just confined to the surface. Therefore a rigid polymer brush layer could not be achieved. Atom transfer radical polymerization (ATRP) method showed the solution to this problem. Polymer brush layers with acceptable thickness could now be achieved for growing polyacrylamide from silica gel. Yet it still suffered from several disadvantages such as the need of an inert atmosphere for polymerization and limited thickness. Many developments have taken place in the past decade which led to improvements in substrate and polymerization methods. This research used non porous sub-micron silica as the substrate and AGET ATRP (Activator generated electron transfer atom transfer radical polymerization) for surface grafting polyacrylamide. Non porous submicron silica has been shown to be a better stationary phase substrate for protein separations than conventional substrates. AGET ATRP enables polymerization to be performed under ambient conditions and in water based solutions which gives thicknesses much higher than conventional ATRP. Data from various analytical techniques showed that within the experimental range the polymerization is linear and has decent control. This means silica nanoparticles coated with polyacrylamide of varying thickness can be produced by varying the reaction time. Linear polymerization kinetics was studied using IR spectroscopy, elemental analysis, ellipsometry, GPC etc. All of them closely agree with each other. Attempts were made to expand the applicability of this novel way of material synthesis. HILIC is known as a premium separation mode for polar analytes. Glycoproteins form an important class of analytes which need better separation columns. Polyacrylamide coated nonporous colloidal silica is shown here to be a better column packing material. Combined results show that AGET ATRP can be a better and simpler alternative to ATRP for grafting polyacrylamide onto silica based substrates. Future efforts can possibly lead to the expansion of the applicability of this method for making materials for many other separation methods.

Yerneni, Charu K.

55

Polyelectrolyte brushes grafted from cellulose nanocrystals using Cu-mediated surface-initiated controlled radical polymerization.  

PubMed

Herein we report the synthesis of cellulose nanocrystals (CNCs) grafted with poly(acrylic acid) (PAA) chains of different lengths using Cu-mediated surface initiated-controlled radical polymerization (SI-CRP). First, poly(tert-butylacrylate) (PtBA) brushes were synthesized; then, subsequent acid hydrolysis was used to furnish PAA brushes tethered onto the CNC surfaces. The CNCs were chemically modified to create initiator moieties on the CNC surfaces using chemical vapor deposition (CVD) and continued in solvent phase in DMF. A density of initiator groups of 4.6 bromine ester groups/nm(2) on the CNC surface was reached, suggesting a dense functionalization and a promising starting point for the controlled/living radical polymerization. The SI-CRP of tert-butylacrylate proceeded in a well-controlled manner with the aid of added sacrificial initiator, yielding polymer brushes with polydispersity values typically well below 1.12. We calculated the polymer brush grafting density to almost 0.3 chains/nm(2), corresponding to high grafting densities and dense polymer brush formation on the nanocrystals. Successful rapid acid hydrolysis to remove the tert-butyl groups yielded pH-responsive PAA-polyelectrolyte brushes bound to the CNC surface. Individually dispersed rod-like nanoparticles with brushes of PtBA or PAA were clearly visualized by AFM and TEM imaging. PMID:21740051

Majoinen, Johanna; Walther, Andreas; McKee, Jason R; Kontturi, Eero; Aseyev, Vladimir; Malho, Jani Markus; Ruokolainen, Janne; Ikkala, Olli

2011-08-01

56

Surface modification of active metals through atom transfer radical polymerization grafting of acrylics  

NASA Astrophysics Data System (ADS)

The objective of this work is to investigate the fundamentals of surface-initiated atom transfer radical polymerization (s-ATRP) on metal substrates. Acrylic polymers were grafted from active metal surfaces such as cold rolled steel (CRS), stainless steel (SS) and nickel (Ni) through s-ATRP. Severe deactivation was found with copper bromide bipyridine catalyst. Controlled polymerization with relatively low polydispersities, 1.18-1.35, was achieved using iron bromide triphenylphosphine catalyst. Polymer films up to 80 nm in thickness were obtained within 80 min. Grafting densities were estimated to be 0.58 chains/nm 2 for CRS-g-PMMA, 0.55 chains/nm 2 for Ni-g-PMMA, 0.18 chains/nm 2 for SS-g-PMMA, and 0.66 chains/nm 2 for SS-g-PDMAEMA. Electrochemical experiments were also carried out to measure the polarization resistance and corrosion potential of CRS-g-PMMA substrates. Metal surfaces with grafted brush polymer coatings showed significant corrosion resistance. This work demonstrated that the surface-initiated ATRP is a versatile means for the surface modification of active metals with well-defined and functionalized polymer brushes.

Gong, Rachel; Maclaughlin, Shane; Zhu, Shiping

2008-08-01

57

Preparation of acrylate IPN copolymer latexes by radiation emulsion polymerization  

NASA Astrophysics Data System (ADS)

Radiation-induced and chemical initiation are compared in the initiation of acrylate emulsion copolymer latexes. The particle diameter, distribution and microstructure are influenced by emulsifier concentration, radiation dose and temperature. The results show that the emulsion particle diameter of radiation polymerization is smaller and better distributed in comparison to using chemical polymerization. In addition, interlude polymer net (IPN) core-shell copolymer latexes are observed by transmission electron microscope (TEM). The bounding face of core-shell acrylate copolymmer texes of radiation polymerization is clearer. The morphology of acrylate IPN copolymer latexes is further investigated.

Wu, Minghong; Zhou, Ruimin; Ma, Zue-Teh; Bao, Borong; Lei, Jianqiu

1997-03-01

58

Syntheses of amine-type adsorbents with emulsion graft polymerization of glycidyl methacrylate  

NASA Astrophysics Data System (ADS)

Glycidyl methacrylate (GMA) which was precursor monomer for the synthesis of metal ion adsorbent was emulsified by surfactant of Tween 20 (Tw-20). The emulsion of 5% GMA in the water was stable for 48 h at Tw-20 concentration of 0.5%. Graft polymerization of GMA on polyethylene fiber was carried out in the emulsion state at various pre-irradiation doses. Degree of grafting (Dg) reached 103%, 301% and 348% for 1 h grafting at 40 °C with pre-irradiation of 10, 30 and 40 kGy, respectively. But the Dg was depressed when the pre-irradiation dose was over 50 kGy since cross-linking occurred simultaneously in the trunk polymer. Dg decreased with increment of Tw-20 concentration in emulsion of 5% GMA at pre-irradiation of 40 kGy. The three kinds of amine-type adsorbents were synthesized by reacting diethylenetriamine (DETA), triethylenetetramine (TETA) and ethylenediamine (EDA) with GMA-grafted polyethylene fiber. The synthesized EDA-type adsorbent had the highest selectivity against U ion and the distribution coefficient was 2.0 × 10 6.

Seko, N.; Bang, L. T.; Tamada, M.

2007-12-01

59

All solid-state polymer electrolytes prepared from a hyper-branched graft polymer using atom transfer radical polymerization  

Microsoft Academic Search

We propose an all solid-state (liquid free) polymer electrolyte (SPE) prepared from a hyper-branched graft copolymer. The graft copolymer consisting of a poly(methyl methacrylate) main chain and poly(ethylene glycol) methyl ether methacrylate side chains was synthesized by atom transfer radical polymerization changing the average chain distance between side chains, side chain length and branched chain length of the proposed structure

Mitsuru Higa; Yukiko Fujino; Taihei Koumoto; Ryousuke Kitani; Satsuki Egashira

2005-01-01

60

Plasma graft-polymerization for synthesis of highly stable hydroxide exchange membrane  

NASA Astrophysics Data System (ADS)

A novel plasma graft-polymerization approach is adopted to prepare hydroxide exchange membranes (HEMs) using cardo polyetherketone powders (PEK-C) and vinylbenzyl chloride. The benzylic chloromethyl groups can be successfully introduced into the PEK-C polymer matrix via plasma graft-polymerization. This approach enables a well preservation in the structure of functional groups and formation of a highly cross-linked structure in the membrane, leading to an improvement on the stability and performance of HEMs. The chemical stabilities, including alkaline and oxidative stability, are evaluated under severe conditions by measuring hydroxide conductivity and weight changes during aging. The obtained PGP-NOH membrane retains 86% of the initial hydroxide conductivity in 6 mol L-1 KOH solution at 60 °C for 120 h, and 94% of the initial weight in 3 wt% H2O2 solution at 60 °C for 262 h. The PGP-NOH membrane also possesses excellent thermal stability (safely used below 120 °C), alcohol resistance (ethanol permeability of 6.6 × 10-11 m2 s-1 and diffusion coefficient of 3.7 × 10-13 m2 s-1), and an acceptable hydroxide conductivity (8.3 mS cm-1 at 20 °C in deionized water), suggesting a good candidate of PGP-NOH membrane for HEMFC applications.

Hu, Jue; Zhang, Chengxu; Jiang, Lin; Fang, Shidong; Zhang, Xiaodong; Wang, Xiangke; Meng, Yuedong

2014-02-01

61

PEG Molecular Net-Cloth Grafted on Polymeric Substrates and Its Bio-Merits  

NASA Astrophysics Data System (ADS)

Polymer brushes and hydrogels are sensitive to the environment, which can cause uncontrolled variations on their performance. Herein, for the first time, we report a non-swelling ``PEG molecular net-cloth'' on a solid surface, fabricated using a novel ``visible light induced surface controlled graft cross-linking polymerization'' (VSCGCP) technique. Via this method, we show that 1) the 3D-network structure of the net-cloth can be precisely modulated and its thickness controlled; 2) the PEG net-cloth has excellent resistance to non-specific protein adsorption and cell adhesion; 3) the mild polymerization conditions (i.e. visible light and room temperature) provided an ideal tool for in situ encapsulation of delicate biomolecules such as enzymes; 4) the successive grafting of reactive three-dimensional patterns on the PEG net-cloth enables the creation of protein microarrays with high signal to noise ratio. Importantly, this strategy is applicable to any C-H containing surface, and can be easily tailored for a broad range of applications.

Zhao, Changwen; Lin, Zhifeng; Yin, Huabing; Ma, Yuhong; Xu, Fujian; Yang, Wantai

2014-05-01

62

PEG Molecular Net-Cloth Grafted on Polymeric Substrates and Its Bio-Merits  

PubMed Central

Polymer brushes and hydrogels are sensitive to the environment, which can cause uncontrolled variations on their performance. Herein, for the first time, we report a non-swelling “PEG molecular net-cloth” on a solid surface, fabricated using a novel “visible light induced surface controlled graft cross-linking polymerization” (VSCGCP) technique. Via this method, we show that 1) the 3D-network structure of the net-cloth can be precisely modulated and its thickness controlled; 2) the PEG net-cloth has excellent resistance to non-specific protein adsorption and cell adhesion; 3) the mild polymerization conditions (i.e. visible light and room temperature) provided an ideal tool for in situ encapsulation of delicate biomolecules such as enzymes; 4) the successive grafting of reactive three-dimensional patterns on the PEG net-cloth enables the creation of protein microarrays with high signal to noise ratio. Importantly, this strategy is applicable to any C-H containing surface, and can be easily tailored for a broad range of applications. PMID:24845078

Zhao, Changwen; Lin, Zhifeng; Yin, Huabing; Ma, Yuhong; Xu, Fujian; Yang, Wantai

2014-01-01

63

Homogeneous ring opening graft polymerization of ?-caprolactone onto xylan in dual polar aprotic solvents.  

PubMed

Homogeneous ring-opening graft polymerization (ROGP) of ?-caprolactone (?-CL) onto xylan was investigated in dual polar aprotic solvents, N,N-dimethylformamide/lithium chloride (DMF/LiCl), N,N-dimethylacetamide/LiCl (DMAc/LiCl), and 1-methyl-2-pyrrolidinone/LiCl (NMP/LiCl). The effects of reaction solvents, temperature, and the molar ratio of ?-CL to anhydroxylose units (AXU) on the degree of substitution (DS) of xylan-graft-poly(?-caprolactone) (xylan-g-PCL) copolymers and the degree of polymerization (DP) of the attached PCL side chains were investigated. FT-IR and NMR analyses provided the evidence of the occurrence of ROGP reaction. The thermal stability of xylan increased upon ROGP reaction due to the increased length of PCL side chains. With the increased attachment of PCL side chains, the tensile strength and Young's modulus of the films decreased, whereas the elongation at break increased. Scanning electron microscopy (SEM) and atomic force microscopy (AFM) observations provided the evidences of the increased film properties due to the attachment of PCL side chains. PMID:25498691

Zhang, Xueqin; Chen, Mingjie; Liu, Chuanfu; Zhang, Aiping; Sun, Runcang

2015-03-01

64

PEG molecular net-cloth grafted on polymeric substrates and its bio-merits.  

PubMed

Polymer brushes and hydrogels are sensitive to the environment, which can cause uncontrolled variations on their performance. Herein, for the first time, we report a non-swelling "PEG molecular net-cloth" on a solid surface, fabricated using a novel "visible light induced surface controlled graft cross-linking polymerization" (VSCGCP) technique. Via this method, we show that 1) the 3D-network structure of the net-cloth can be precisely modulated and its thickness controlled; 2) the PEG net-cloth has excellent resistance to non-specific protein adsorption and cell adhesion; 3) the mild polymerization conditions (i.e. visible light and room temperature) provided an ideal tool for in situ encapsulation of delicate biomolecules such as enzymes; 4) the successive grafting of reactive three-dimensional patterns on the PEG net-cloth enables the creation of protein microarrays with high signal to noise ratio. Importantly, this strategy is applicable to any C-H containing surface, and can be easily tailored for a broad range of applications. PMID:24845078

Zhao, Changwen; Lin, Zhifeng; Yin, Huabing; Ma, Yuhong; Xu, Fujian; Yang, Wantai

2014-01-01

65

Surface graft polymerization of SU-8 for bio-MEMS applications  

NASA Astrophysics Data System (ADS)

There is currently increasing interest in using SU-8 photoresist to build microstructures for micro-electro-mechanical systems (MEMS). This report describes an effective bench-top method to modify the surface properties of SU-8 photoresist. This strategy relies on the residual epoxide groups present on the surface of SU-8 following fabrication. These epoxide groups are converted into hydroxyl groups by oxidation with a high concentration of cerium(IV) ammonium nitrate (CAN) and nitric acid. Subsequently the surface hydroxyl groups are used as initiation sites for graft polymerization catalyzed by CAN in the presence of acid. A number of water-soluble polymers including poly(acrylic acid), poly(acrylamide), poly(ethylene glycol) were successfully grafted onto SU-8. The presence of surface-linked polymers was confirmed by contact angle measurements, attenuated total reflection-Fourier transform infrared spectroscopy and toluidine blue adsorption. This method was particularly useful for tailoring the surface properties of complex or enclosed microstructures, for example, microfluidic channels. In addition the grafted polymers could serve as sites for high density protein immobilization or cell attachment on Bio-MEMS.

Wang, Yuli; Pai, Jeng-Hao; Lai, Hsuan-Hong; Sims, Christopher E.; Bachman, Mark; Li, G. P.; Allbritton, Nancy L.

2007-07-01

66

A mild strategy to encapsulate enzyme into hydrogel layer grafted on polymeric substrate.  

PubMed

Although the hydrogel network has been widely investigated as a carrier for enzyme immobilization, to in situ encapsulate enzymes into a hydrogel network in an efficient, practical, and active way is still one of the great challenges in the field of biochemical engineering. Here, we report a new protocol to address this issue by encapsulating enzyme into poly(ethylene glycol) (PEG) hydrogel network grafted on polymeric substrates. In our strategy, isopropyl thioxanthone semipinacol (ITXSP) dormant groups were first planted onto the surface of a plastic matrix with low density polyethylene (LDPE) film as a model by a UV-induced abstracting hydrogen-coupling reaction. As a proof of concept, lipase, which could catalyze esterification of glucose with palmitic acid, then was in situ net-immobilized into a PEG-based hydrogel network layer through a visible light-induced surface controlled/living graft cross-linking polymerization. This strategy demonstrates the following novel significant merits: (1) in comparison with the UV irradiation or high temperature, the visible light and room temperature used provide a friendly condition to maintain activity of enzyme during immobilization; (2) the uniqueness of controlled/living cross-linking polymerization not only makes it easy to form a uniform PEG hydrogel network, which is a benefit to avoid the leakage of net-immobilizing enzyme, but also to tune the net-thickness or capacity to accommodate enzyme; and (3) as compared to systems of nanoparticles and porous matrixes, the flexible/robust end-products of the surface net-immobilizing enzyme with polymer film are more suitable to be applied in a bioreactor due to their features of easier separation and reuse. We confirmed that this catalytic film could retain almost all of its initial activity after seven batches of 24 h esterifications. The proposed strategy provides an extremely simple, effective, and flexible method for enzyme immobilization. PMID:25489918

Zhu, Xing; Ma, Yuhong; Zhao, Changwen; Lin, Zhifeng; Zhang, Lihua; Chen, Ruichao; Yang, Wantai

2014-12-23

67

Strategies and Techniques to Enhance the In Situ Endothelialization of Small-Diameter Biodegradable Polymeric Vascular Grafts  

PubMed Central

Due to the lack of success in small-diameter (<6?mm) prosthetic vascular grafts, a variety of strategies have evolved utilizing a tissue-engineering approach. Much of this work has focused on enhancing the endothelialization of these grafts. A healthy, confluent endothelial layer provides dynamic control over homeo-stasis, influencing and preventing thrombosis and smooth muscle cell proliferation that can lead to intimal hyperplasia. Strategies to improve endothelialization of biodegradable polymeric grafts have encompassed both chemical and physical modifications to graft surfaces, many focusing on the recruitment of endothelial and endothelial progenitor cells. This review aims to provide a compilation of current and developing strategies that utilize in situ endothelialization to improve vascular graft outcomes, providing a context for the future directions of vascular tissue-engineering strategies that do not require preprocedural cell seeding. PMID:23252992

Hibino, Narutoshi; Fisher, John P.

2013-01-01

68

Salt splitting with radiation grafted PVDF membranes  

Microsoft Academic Search

Sulphonated PVDF cation-exchange membranes have been formulated for the splitting of sodium sulphate by electrohydrolysis. Three membranes with different degree of grafting were tested in a two-compartment membrane cell. The effect of flow rate, current density and salt concentration on the performance of each membrane is described. The different flow conditions in front of the membranes did not significantly affect

N. Tzanetakis; W. M. Taama; K. Scott; J. Varcoe; R. S. Slade

2003-01-01

69

Radiation grafting of NIPAAm on PVDF nuclear track membranes  

Microsoft Academic Search

Polymer surface modifications are obtained by the application of radiation treatments and other physico-chemical methods: fragment fission (ff) or ion implantation, etching and grafting procedure. Poly vinylidene fluoride (PVDF) foils were irradiated during different times to produce pores of different diameters through the foils. In this way, nuclear track membranes (NTM) were produced with different track diameters and track numbers.

Ruben Mazzei; Eduardo Smolko; Daniel Tadey; Laura Gizzi

2000-01-01

70

Microwave CO2 plasma-initiated vapour phase graft polymerization of acrylic acid onto polytetrafluoroethylene for immobilization of human thrombomodulin.  

PubMed

The functionalization of polytetrafluoroethylene (PTFE) for human thrombomodulin (hTM) binding has been achieved by CO2 plasma activation and subsequent vapour phase graft polymerization of acrylic acid (AA). The PTFE surfaces after CO2 plasma treatment, AA grafting and hTM immobilization were characterized by attenuated total reflection Fourier transform infrared (ATR-FTIR) spectroscopy, X-ray photoelectron spectroscopy (XPS) and electron spin resonance (ESR) spectroscopy, as well as by zeta potential and wetting measurements to quantitatively control each step of modification. The activity of immobilized hTM was estimated by the protein C activation test. PMID:9259510

Vasilets, V N; Hermel, G; König, U; Werner, C; Müller, M; Simon, F; Grundke, K; Ikada, Y; Jacobasch, H J

1997-09-01

71

Radiation-induced grafting of acrylamide onto guar gum in aqueous medium: Synthesis and characterization of grafted polymer guar-g-acrylamide  

NASA Astrophysics Data System (ADS)

Mutual radiation grafting technique has been applied to carry out grafting of acrylamide (AAm) onto guar gum (GG) using high-energy Co 60? radiation to enhance its flocculating properties for industrial effluents. The grafted product was characterized using analytical probes like elemental analysis, thermal analysis, Fourier transformed infrared (FTIR), X-ray diffraction (XRD) and scanning electron microscope (SEM). The grafting extent was observed to decrease with the dose rate and increase with the concentration of AAm. Thermo gravimetric analysis (TGA) of grafted and ungrafted samples indicated better stability of grafted product. ? and microwave radiation effect on grafted and virgin GG has also been reported.

Biswal, Jayashree; Kumar, Virendra; Bhardwaj, Y. K.; Goel, N. K.; Dubey, K. A.; Chaudhari, C. V.; Sabharwal, S.

2007-10-01

72

Controlled grafting from poly(vinylidene fluoride) microfiltration membranes via reverse atom transfer radical polymerization and antifouling properties  

Microsoft Academic Search

A reverse atom transfer radical polymerization (RATRP) with benzoyl peroxide (BPO)\\/CuCl\\/2,2-bipyridine (Bpy) was applied onto grafting of poly(methyl methacrylate) (PMMA) and poly(poly(ethylene glycol) methyl ether methacrylate) (PPEGMA) from poly(vinylidene fluoride) (PVDF) microfiltration (MF) membrane surfaces, including the pore surfaces. The introduction of peroxide and hydroperoxide groups onto the PVDF membranes was achieved by ultraviolet (UV) irradiation in nitrogen, followed by

Yiwang Chen; Qilan Deng; Jichun Xiao; Huarong Nie; Lichuan Wu; Weihua Zhou; Biwu Huang

2007-01-01

73

Salt splitting with radiation grafted PVDF anion-exchange membrane  

Microsoft Academic Search

A radiation grafted poly(vinylidene fluoride) anion-exchange membrane has been formulated and its behaviour is analysed through the splitting of sodium sulphate by electrohydrolysis. Experiments carried out in a two-compartment membrane electrolysis cell, investigated the influence of flow rate, current density and salt concentration on the performance of the membrane. The different flow conditions had a small influence on current efficiencies,

N. Tzanetakis; J. Varcoe; R. S. Slade; K. Scott

2003-01-01

74

Space radiation resistant transparent polymeric materials  

NASA Technical Reports Server (NTRS)

A literature search in the field of ultraviolet and charged particle irradiation of polymers was utilized in an experimental program aimed at the development of radiation stable materials for space applications. The rationale utilized for material selection and the synthesis, characterization and testing performed on several selected materials is described. Among the materials tested for ultraviolet stability in vacuum were: polyethyleneoxide, polyvinylnaphthalene, and the amino resin synthesized by the condensation of o-hydroxybenzoguanamine with formaldehyde. Particularly interesting was the radiation behavior of poly(ethyleneoxide), irradiation did not cause degradation of optical properties but rather an improvement in transparency as indicated by a decrease in solar absorptance with increasing exposure time.

Giori, C.; Yamauchi, T.

1977-01-01

75

Graft polymerization of acrylic acid and methacrylic acid onto poly(vinylidene fluoride) powder in presence of metallic salt and sulfuric acid  

NASA Astrophysics Data System (ADS)

Poly(vinylidene fluoride) (PVDF) powder was grafted with acrylic acid (AAc) or methacrylic acid (MAA) by the pre-irradiation induced graft polymerization technique. The presence of graft chains was proven by FT-IR spectroscopy. The degree of grafting (DG) was calculated by the acid-base back titration method. The synergistic effect of acid and Mohr's salt on the grafting kinetics was examined. The results indicated that adding sulfuric acid and Mohr's salt simultaneously in AAc or MAA solutions led to a strong enhancement in the degree of grafting. The grafted PVDF powder was cast into microfiltration (MF) membranes using the phase inversion method and some properties of the obtained MF membranes were characterized.

Deng, Bo; Yu, Yang; Zhang, Bowu; Yang, Xuanxuan; Li, Linfan; Yu, Ming; Li, Jingye

2011-02-01

76

Radiation-induced grafting of styrene into radiation-modified fluoropolymer films  

Microsoft Academic Search

Poly(tetrafluoroethylene) (PTFE), poly(tetrafluoroethylene-co-hexafluoropropylene) (FEP) and poly(tetrafluoroethylene-co-perfluoropropylvinyl ether) (PFA) films were modified by electron beam irradiation in the molten state. These radiation-modified films and original films were irradiated in vacuum at room temperature to initiate the grafting of styrene in the subsequent step. The grafting of styrene into the fluoropolymer films was proved by FT-IR spectroscopy. The influence of cross-linking dose,

Uwe Lappan; Uwe Geißler; Steffi Uhlmann

2005-01-01

77

Development of hydrogels by radiation induced polymerization for use in slow drug delivery  

NASA Astrophysics Data System (ADS)

In the present work, in order to improve the drug release profile of indinavir sulfate, a potent inhibitor of HIV protease, controlled drug delivery systems in the form of hydrogels have been designed by a radiation graft polymerization method. These hydrogels have been prepared by using dietary fiber psyllium and binary monomers mixture of acrylamide (AAm) and 2-acrylamido-2-methylpropanesulfonic acid (AMPSA). These polymers have been characterized with cryo-SEMs, FTIR, XRD and swelling studies. The swelling of hydrogels has been determined in solution of different pH, temperature and [NaCl]. in vitro release studies of model drug indinavir sulfate in different pH have been carried out to determine the drug release mechanism. The release of dug occurred through non-Fickian mechanism.

Singh, Baljit; Bala, R.

2014-10-01

78

Radiation-induced grafting of cellulose for adsorption of hazardous water pollutants: A review  

NASA Astrophysics Data System (ADS)

This review paper briefly introduces the radiation chemistry of cellulose, the different grafting techniques used, and the methods of characterization of the grafted material. It shows the application of the grafted polymer for the removal of water pollutants and also the regeneration of the adsorbent.

Wojnárovits, L.; Földváry, Cs. M.; Takács, E.

2010-08-01

79

Radiation-induced grafting of cellulose for adsorption of hazardous water pollutants: A review  

Microsoft Academic Search

This review paper briefly introduces the radiation chemistry of cellulose, the different grafting techniques used, and the methods of characterization of the grafted material. It shows the application of the grafted polymer for the removal of water pollutants and also the regeneration of the adsorbent.

L. Wojnárovits; Cs. M. Földváry; E. Takács

2010-01-01

80

Crystal structure and mechanical properties of UHMWPE-g-PMA fiber prepared by radiation grafting  

NASA Astrophysics Data System (ADS)

Methyl acrylate (MA) monomer was grafted onto ultra-high molecular weight polyethylene (UHMWPE) fibers by ?-ray pre-irradiation induced graft polymerization. The grafting of MA on UHMWPE fiber was confirmed by thermogravimetric analysis and Fourier-transform infrared spectroscopy. The degree of grafting (DG) increased with an increase in absorbed dose and reached a significantly high value (approximately 200%) at 100 kGy. Scanning electron microscopy analysis revealed that the surface of the UHMWPE-g-PMA fibers was covered by the MA grafting layer and became rough. The monoclinic crystalline and orientated intermediate phases were disordered by the grafting chains such that degree of orientation declined gradually with increasing DG. The tensile strength of UHMWPE-g-PMA fiber decreased with increasing dose but was independent of DG, whereas the fiber modulus declined with DG. UHMWPE-g-PMA fiber that possesses desirable mechanical properties could be obtained at a dose of less than 10 kGy.

Xing, Zhe; Wang, Mouhua; liu, Weihua; Hu, Jiangtao; Wu, Guozhong

2013-05-01

81

The tolerance of skin grafts to postoperative radiation therapy in patients with soft-tissue sarcoma  

SciTech Connect

During the last ten years at the National Cancer Institute, 11 patients have received 12 courses of postoperative adjuvant radiation therapy to skin grafts used for wound closure after the resection of soft-tissue sarcomas. The intervals between grafting and the initiation of radiation ranged between 3 and 20 weeks, and 4 patients received chemotherapy at the same time as their radiation. Ten of the 12 irradiated grafts remained intact after the completion of therapy. One graft had several small persistently ulcerated areas that required no further surgical treatment, and one graft required a musculocutaneous flap for reconstruction of a persistent large ulcer. Acute radiation effects on the grafted skin sometimes developed at slightly lower doses than usually seen with normal skin, but these acute effects necessitated a break in therapy on only five occasions. Concurrent chemotherapy and a relatively short interval between grafting and the initiation of radiation seemed to contribute to more severe radiation reactions. This experience indicates that postoperative adjuvant radiation therapy can be delivered to skin grafted areas without undue fear of complications, especially if the graft is allowed to heal adequately prior to initiating therapy and if chemotherapy is not given in conjunction with radiation.

Lawrence, W.T.; Zabell, A.; McDonald, H.D. (National Cancer Institute, Bethesda, MD (USA))

1986-03-01

82

Self-assembly and chiroptical property of poly(N-acryloyl-L-amino acid) grafted celluloses synthesized by RAFT polymerization.  

PubMed

Three amphiphilic poly(N-acryloyl-L-amino acid) grafted celluloses were prepared by RAFT polymerization of N-acryloyl-L-amino acid, where amino acid is alanine, proline or glutamic acid, onto cellulose backbones. The chemical structure and solution properties of the brush copolymers were characterized with FTIR, NMR and wide angle X-ray diffraction (WAXD). The thermal stability of the brush copolymers was estimated by thermal gravimetric analysis (TGA). Circular dichroism (CD) and specific rotation measurements confirmed that these grafted celluloses had characteristic chiroptical properties. The amphiphilic brush copolymers self-assembled into micelles in the aqueous solution as confirmed by transmission electron microscopy (TEM) and dynamic light scattering (DLS) analyses. The micellar aggregates showed a tunable pH-responsive property and disaggregated to form unimolecular micelles at higher pH in diluted solutions. The brush copolymers have potential applications in controlled drug release and high-performance liquid chromatography, and so forth. PMID:25498640

Liu, Yadong; Jin, Xiaosa; Zhang, Xiaosa; Han, Miaomiao; Ji, Shengxiang

2015-03-01

83

Radiation grafted poly(vinylidene fluoride)- graft -polystyrene sulfonic acid membranes for fuel cells: Structure-property relationships  

Microsoft Academic Search

Structure-property relationships for poly(vinylidene fluoride)-graft-polystyrene sulfonic acid (PVDF-g-PSSA) fuel cell membranes prepared by a single step method involving radiation-induced grafting of sodium styrene sulfonate\\u000a (SSS) onto electron beam (EB) irradiated poly(vinylidene fluoride) (PVDF) films were established. The physico-chemical properties\\u000a of the membranes such as ion exchange capacity, water swelling and proton conductivity were correlated with the degree of\\u000a grafting (G,

Mohamed Nasef; Hamdani Saidi; Khairulzaman Mohd Dahlan

2010-01-01

84

Comparison of polymerically stabilized PEG-grafted liposomes and physically adsorbed carboxymethylchitin and carboxymethyl\\/glycolchitin liposomes for biological applications  

Microsoft Academic Search

The stabilities of two types of polymerically stabilized liposomes consisting of PEG-grafted (DSPC:CHOL:DSPE-PEG1900, 5:4:1) and physically adsorbed carboxymethylchitin (CMC) and carboxymethyl\\/glycolchitin (CO) are compared. The polyelectrolyte is adsorbed on positive (DSPC:CHOL:DMTAP, 5:4:1) and neutral (DSPC:CHOL, 1:1) liposomes at different molecular weights (Mw). In PBS buffer (I=154mm, pH=7.4) the theoretical stability ratios (W) calculated using the classical DLVO Theory, indicate that

M Mobed; T. M. S Chang

1998-01-01

85

Radiation-grafted, chemically modified membranes part I - Synthesis of a selective aluminum material  

NASA Astrophysics Data System (ADS)

Polymeric membranes were styrene grafted by irradiation methods and the obtained material was chemically modified to become aluminum selective. For this purpose, polymeric substrates of PVC (polyvinyl chloride) and PP (polypropylene) were styrene grafted mutually by gamma and electron beam irradiation. The modification process includes three basic reaction paths: Friedel-Crafts acylation, 2-methylanisole coupling and a final oxidation to achieve aluminum selectivity. Although this specific chemical modification in derivatives of polystyrene is not new, the new challenge is to obtain a selective material where original membrane characteristics (physical shape and mechanical resistance) are minimally conserved after such an aggressive treatment.

Bazante-Yamaguishi, Renata; Moura, Eduardo; Manzoli, José E.; Geraldo, Aurea B. C.

2014-01-01

86

Catalytic polymerization and facile grafting of poly(furfuryl alcohol) to single-wall carbon nanotube: preparation of nanocomposite carbon.  

PubMed

A nanocomposite carbon was prepared by grafting a carbonizable polymer, poly(furfuryl alcohol) (PFA), to a single-wall carbon nanotube (SWNT). The SWNT was first functionalized with arylsulfonic acid groups on the sidewall via a method using a diazonium reagent. Both Raman and FTIR spectroscopies were used to identify the functional groups on the nanotube surface. HRTEM imaging shows that the SWNT bundles are exfoliated after functionalization. Once this state of the SWNTs was accomplished, the PFA-functionalized SWNT (PFA-SWNT) was prepared by in situ polymerization of furfuryl alcohol (FA). The sulfonic acid groups on the surface of the SWNT acted as a catalyst for FA polymerization, and the resulting PFA then grafted to the SWNTs. The surfaces of the SWNTs converted from hydrophilic to hydrophobic when they were wrapped with PFA. The formation of the polymer and the attraction between it and the sulfonic acid groups were confirmed by IR spectra. A nanocomposite carbon was generated by heating the PFA-SWNT in argon at 600 degrees C, a process during which the PFA was transformed to nanoporous carbon (NPC) and the sulfonic acid groups were cleaved from the SWNT. Based upon the Raman spectra and HRTEM images of the composite, it is concluded that SWNTs survive this process and a continuous phase is formed between the NPC and the SWNT. PMID:16925450

Yi, Bo; Rajagopalan, Ramakrishnan; Foley, Henry C; Kim, Un Jeong; Liu, Xiaoming; Eklund, Peter C

2006-08-30

87

Formation of monodisperse PMMA particles by radiation-induced dispersion polymerization—I. Synthesis and polymerization kinetics  

NASA Astrophysics Data System (ADS)

Highly monodisperse poly(methyl methacrylate) microparticles were directly prepared by radiation-induced dispersion polymerization at room temperature in aqueous alcohol media using poly( N-vinylpyrrolidone) as a steric stabilizer. Monomer conversion was studied dilatometrically and polymer molecular weight was determined viscometrically. The gel effect was evident from the increase of the molecular weight with conversion and also from the percentage conversion vs. time curves. The influences of dose rate, monomer concentration, stabilizer content, medium polarity, polymerization temperature on the polymerization rate and the molecular weight of polymer have been examined. It was found that the overall activation energy for the rate of polymerization is 18.44 kJ/mol (10-25°C). Based on the experimental results, the polymerization mechanisms were discussed.

Ye, Qiang; Ge, Xuewu; Zhang, Zhicheng

2003-01-01

88

Radiation grafting of methyl methacrylate onto polyethylene separators for lithium secondary batteries  

NASA Astrophysics Data System (ADS)

Micro-porous polyethylene separator was modified by radiation grafting of methyl methacrylate in order to improve its affinity with a liquid electrolyte. The degree of grafting (DOG) increased with the monomer concentration and grafting time. The morphological change of the modified separator was investigated by scanning electron microscopy. The degree of crystallinity upon grafting was reduced due to the formation of an amorphous PMMA layer. The electrolyte uptake and the ionic conductivity of the separator increased with an increase in the DOG. The ionic conductivity reached 2.0 mS/cm for the grafted polyethylene separator with 127 wt% DOG.

Gwon, Sung-Jin; Choi, Jae-Hak; Sohn, Joon-Yong; An, Sung-Jun; Ihm, Young-Eon; Nho, Young-Chang

2008-08-01

89

A novel polymeric flocculant based on polyacrylamide grafted inulin: aqueous microwave assisted synthesis.  

PubMed

Polyacrylamide grafted inulin (In-g-PAM) was synthesized via aqueous microwave assisted method (using ceric ammonium nitrate in synergism with microwave in aqueous medium). The intended grafting of the PAM chains on polysaccharide backbone was confirmed through standard physicochemical characterization techniques, namely intrinsic viscosity measurement, Fourier transform infrared (FTIR) spectroscopy, elemental analysis (C, H, N and O), thermogravimetric analysis (TGA) and scanning electron microscopy (SEM) studies. Flocculation efficacy of various grades of synthesized grafted product was studied in coal fines suspension, in relation to inulin (parent polysaccharide). This was done utilizing jar test and settling test procedure, towards possible application as a flocculant for coal washery effluents. PMID:24274474

Rahul, Rahul; Jha, Usha; Sen, Gautam; Mishra, Sumit

2014-01-01

90

Novel media for chromatography, immobilization and hemo-perfusion using radiation grafting technique  

NASA Astrophysics Data System (ADS)

A radiation grafting technique has been developed using simultaneously different vinylmonomers and solvents or swelling agents. Grafting is applied to modify polyamide-6 in microbead form leading to matrices which can favourably be used for affinity chromatography, immobilization and as immunoadsorbents. By appropriately combining monomers carrying diverse functional groups, matrices are obtained with high binding capacities. Affinity chromatography and enzyme/biomolecule immobilization tests have been conducted using epoxy-grafted matrices. The radiation modified media show binding capacities 5 to 20times higher than commercial products. Grafted polyamide, to which a blood group hapten is coupled, is used as immunosorbent for blood group A antibodies.

Müller-Schulte, D.; Thomas, H. G.

91

Novel Diblock Copolymer-Grafted Multiwalled Carbon Nanotubes via a combination of Living and Controlled/Living Surface Polymerizations  

SciTech Connect

Diels Alder cycloaddition reactions were used to functionalize multiwalled carbon nanotubes (MWNTs) with 1-benzocylcobutene-10-phenylethylene (BCB-PE) or 4-hydroxyethylbenzocyclobutene (BCB-EO). The covalent functionalization of the nanotubes with these initiator precursors was verified by FTIR and thermogravimetric analysis (TGA). After appropriate transformations/additions, the functionalized MWNTs were used for surface initiated anionic and ring opening polymerizations of ethylene oxide and e-caprolactone (e-CL), respectively. The OH-end groups were transformed to isopropylbromide groups by reaction with 2-bromoisobutyryl bromide, for subsequent atom transfer radical polymerization of styrene or 2-dimethylaminoethyl methacrylate to afford the final diblock copolymers. 1H NMR, differential scanning calorimetry (DSC), TGA, and transmission electron microscopy (TEM) were used for the characterization of the nanocomposite materials. TEM images showed the presence of a polymer layer around the MWNTs as well as the dissociation of MWNT bundles. Consequently, this general methodology, employing combinations of different polymerization techniques, increases the diversity of diblocks that can be grafted from MWNTs.

Priftis, Dimitrios [ORNL; Sakellariou, Georgios [ORNL; Mays, Jimmy [University of Tennessee, Knoxville (UTK); Hadjichristidis, Nikos [University of Athens, Athens, Greece

2010-01-01

92

Transparent Metal-Salt-Filled Polymeric Radiation Shields  

NASA Technical Reports Server (NTRS)

"COR-RA" (colorless atomic oxygen resistant -- radiation shield) is the name of a transparent polymeric material filled with x-ray-absorbing salts of lead, bismuth, cesium, and thorium. COR-RA is suitable for use in shielding personnel against bremsstrahlung radiation from electron-beam welding and industrial and medical x-ray equipment. In comparison with lead-foil and leaded-glass shields that give equivalent protection against x-rays (see table), COR-RA shields are mechanically more durable. COR-RA absorbs not only x-rays but also neutrons and rays without adverse effects on optical or mechanical performance. The formulation of COR-RA with the most favorable mechanical-durability and optical properties contains 22 weight percent of bismuth to absorb x-rays, plus 45 atomic percent hydrogen for shielding against neutrons.

Edwards, David; Lennhoff, John; Harris, George

2003-01-01

93

Radiation-grafting of acrylamide onto silicone rubber films for diclofenac delivery  

NASA Astrophysics Data System (ADS)

This work focuses on the pre-irradiation grafting of acrylamide (AAm) onto silicone rubber films (SR) and evaluates the effect of gamma-ray radiation conditions on the grafting yield, which in turn may influence the performance of the grafted materials as components of drug-eluting devices. Pristine and modified SR were characterized using FTIR-ATR, DSC, TGA, swelling, and water contact angle analysis in order to elucidate the effects of AAm grafting onto SR. Grafted films with content in AAm ranging from 0.81% to 22.20% showed excellent cytocompatibility against fibroblasts, and capability to uptake the anti-inflammatory drug diclofenac. Amount of drug loaded directly correlated with the grafting degree of the films. Drug release studies were performed at pH 7.4 and 37 °C (physiological conditions). Most grafted films released the drug in a sustained way for at least three hours.

Magańa, Hector; Palomino, Kenia; Cornejo-Bravo, Jose M.; Alvarez-Lorenzo, Carmen; Concheiro, Angel; Bucio, Emilio

2015-02-01

94

Construction of stable polymeric vesicles based on azobenzene and beta-cyclodextrin grafted poly(glycerol methacrylate)s for potential applications in colon-specific drug delivery.  

PubMed

Polymeric vesicles constructed from cyclodextrin- and azobenzene-grafted poly(glycidyl methacrylate)s showed excellent stability owing to the multiple host-guest complexation. Upon culturing in Na2S2O4-contained buffer solution, cargo-loaded vesicles disassembled, for potential applications in colon-specific drug delivery. PMID:25692460

Gu, Wen-Xing; Li, Qing-Lan; Lu, Hongguang; Fang, Lei; Chen, Qixian; Yang, Ying-Wei; Gao, Hui

2015-03-01

95

Surface modification of calcium carbonate: radical graft polymerization of vinyl monomers onto calcium carbonate surface initiated by azo groups introduced onto the surface  

Microsoft Academic Search

—The preparation of calcium carbonate modified by 12-hydroxystearate groups and the grafting of polymers onto the surface by the polymerization of vinyl monomers initiated by azo groups introduced onto the surface were investigated. The preparation of calcium carbonate modified by 12-hydroxystearate was achieved by the reaction of calcium chloride with sodium carbonate containing a small amount of sodium 12-hydroxystearate. The

Yukio Shirai; Kazuyo Seno; Takamitsu Da; Norio Tsubokawa

1996-01-01

96

Plasma-induced graft-polymerization of polyethylene glycol acrylate on polypropylene films: chemical characterization and evaluation of the protein adsorption.  

PubMed

This work deals with the optimization of argon plasma-induced graft-polymerization of polyethylene glycol acrylate (PEGA) on polypropylene (PP) films in order to obtain surfaces with a reduced protein adsorption for possible biomedical applications. To this end, we examined the protein adsorption on the treated and untreated surfaces. The graft-polymerization process consisted of four steps: (a) plasma pre-activation of the PP substrates; (b) immersion in a PEGA solution; (c) argon plasma-induced graft-polymerization; (d) washing and drying of the samples. The efficiency of these processes was evaluated in terms of the amount of grafted polymer, coverage uniformity and substrates wettability. The process was monitored by contact angle measurements, attenuated total reflection Fourier transform infrared spectroscopy (ATR-FTIR), X-ray Photoelectron Spectroscopy (XPS) and atomic force microscopy (AFM) analyses. The stability of the obtained thin films was evaluated in water and in Phosphate Buffer Saline (PBS) at 37 degrees C. The adsorption of fibrinogen and green fluorescent protein (GFP)--taken as model proteins--on the differently prepared surfaces was evaluated through a fluorescence approach using laser scanning confocal microscopy with photon counting detection. After plasma treatments of short duration, the protein adsorption decreases by about 60-70% with respect to that of the untreated film, while long plasma exposure resulted in a higher protein adsorption, due to damaging of the grafted polymer. PMID:19822326

Zanini, Stefano; Riccardi, Claudia; Grimoldi, Elisa; Colombo, Claudia; Villa, Anna Maria; Natalello, Antonino; Gatti-Lafranconi, Pietro; Lotti, Marina; Doglia, Silvia Maria

2010-01-01

97

Grafting of poly(ethylene glycol) monoacrylates on polycarbonateurethane by UV initiated polymerization for improving hemocompatibility.  

PubMed

Poly(ethylene glycol) monoacrylates (PEGMAs) with a molecular weight between 400 and 1,000 g mol(-1) were grafted by ultraviolet initiated photopolymerization on the surface of polycarbonateurethane (PCU) for increasing its hydrophilicity and improving its hemocompatibility. The surface-grafted PCU films were characterized by Fourier transformation infrared spectroscopy, X-ray photoelectron spectroscopy, water contact angle, scanning electron microscopy (SEM) and atomic force microscopy measurements. The surface properties of the modified films were studied in dry and wetted state. Blood compatibility of the surfaces was evaluated by platelet adhesion tests and adhered platelets were determined by SEM. The results showed that the hydrophilicity of the films had been increased significantly by grafting PEGMAs, and platelets adhesion onto the film surface was obviously suppressed. Furthermore, the molecular weight of PEGMAs had a great effect on the hydrophilicity and hemocompatibility of the PCU films after surface modification and increased with increasing molecular weight of PEGMAs. PMID:22661245

Feng, Yakai; Zhao, Haiyang; Behl, Marc; Lendlein, Andreas; Guo, Jintang; Yang, Dazhi

2013-01-01

98

Radiation-induced polymerization for the immobilization of penicillin acylase  

SciTech Connect

The immobilization of Escherichia coli penicillin acylase was investigated by radiation-induced polymerization of 2-hydroxyethyl methacrylate at low temperature. A leak-proof composite that does not swell in water was obtained by adding the cross-linking agent trimethylolpropane trimethacrylate to the monomer-aqueous enzyme mixture. Penicillin acylase, which was immobilized with greater than 70% yield, possessed a higher Km value toward the substrate 6-nitro-3-phenylacetamidobenzoic acid than the free enzyme form (Km = 1.7 X 10(-5) and 1 X 10(-5) M, respectively). The structural stability of immobilized penicillin acylase, as assessed by heat, guanidinium chloride, and pH denaturation profiles, was very similar to that of the free-enzyme form, thus suggesting that penicillin acylase was entrapped in its native state into aqueous free spaces of the polymer matrix.

Boccu, E.; Carenza, M.; Lora, S.; Palma, G.; Veronese, F.M.

1987-06-01

99

Zwitterionic sulfobetaine-grafted poly(vinylidene fluoride) membrane surface with stably anti-protein-fouling performance via a two-step surface polymerization  

NASA Astrophysics Data System (ADS)

A zwitterionic polymer, poly(3-(methacryloylamino) propyl-dimethyl-(3-sulfopropyl) ammonium hydroxide) (poly(MPDSAH)) was successfully grafted in high density from the surface of poly(vinylidene fluoride) (PVDF) hollow fiber membrane via a two-step polymerization. Poly(2-hydroxyethyl methacrylate) (poly(HEMA)) chains were firstly grafted from outside surface of PVDF membrane through atom transfer radical polymerization (ATRP) to provide the initiation sites for subsequent cerium (Ce (IV))-induced graft copolymerization of polyMPDSAH in the presence of N,N'-ethylene bisacrylamide (EBAA) as a cross-linking agent. Attenuated total reflectance-Fourier transform infrared (ATR-FTIR) spectroscopy, X-ray photoelectron spectroscopy (XPS) confirmed that the EBAA could stimulate zwitterionic polymers grafting onto the membrane surface. The dense poly(MPDSAH) layers on the PVDF membrane surface were revealed by the scanning electron microscope (SEM). The mechanical property of PVDF membrane was improved by the zwitterionic surface layers. The gravimetry results indicated the grafting amount increased to 520 ?g/cm2 for a copolymerization time of more than 3 h. Static and dynamic water contact angle measurements showed that the surface hydrophilicity of the PVDF membranes was significantly enhanced. As the grafting amount reached 513 ?g cm-2, the value of contact angle dropped to 22.1° and the amount of protein adsorption decreased to zero. The cyclic experiments for BSA solution filtration demonstrated that the extent of protein fouling was significantly reduced and most of the fouling was reversible. The grafted polymer layer on the PVDF membrane showed a good stability during the membrane cleaning process. The experimental results concluded a good prospect in obtaining the sulfobetaine-modified PVDF membranes with high mechanical strength, good anti-protein-fouling performance, and long-term stability via the two-step polymerization.

Li, Qian; Bi, Qiu-Yan; Zhou, Bo; Wang, Xiao-Lin

2012-03-01

100

Immobilization of enzymes and antibodies to radiation grafted polymers for therapeutic and diagnostic applications  

NASA Astrophysics Data System (ADS)

Pre-irradiation and mutual radiation grafting were employed to produce poly(methacrylic acid) (MAAc) hydrogels on polypropylene/polyethylene (PP/PE) copolymer films, PP films and porous PP fibers of a plasma filter. A diphenyl picryl hydrazyl (DPPH) assay was developed to measure the surface peroxide concentration of the pre-irradiated PP/PE films prior to grafting. Mutually grafted porous PP fibers were used for subsequent immobilization of L-asparaginase while the mutually grafted PP/PE films were used to immobilize a schistosoma monoclonal antibody.

Hoffman, Allan S.; Gombotz, Wayne R.; Uenoyama, Satoshi; Dong, Liang C.; Schmer, Gottfried

101

Functionalization of nanochannels by radio-induced grafting polymerization on PET track-etched membranes  

NASA Astrophysics Data System (ADS)

The application of swift-heavy ion bombardment to polymers is a well-established technique to manufacture micro- and nanopores onto polymeric films to obtain porous membranes. A few years ago, it was realized that, during ion bombardment, the high energy deposition along the ion path through the polymer reached cylindrical damage regions corresponding to the core trace and the penumbra. After the etching procedure, there are still enough active sites left in the penumbra that can be used to initiate a polymerization process selectively inside the membrane pores.

Soto Espinoza, S. L.; Arbeitman, C. R.; Clochard, M. C.; Grasselli, M.

2014-01-01

102

Electrospun nanofiber scaffolds and plasma polymerization: a promising combination towards complete, stable endothelial lining for vascular grafts.  

PubMed

In the quest to reduce risk of thrombosis in vascular grafts, it is essential to provide a surface with morphological and mechanical properties close to those of the extracellular matrix beneath the luminal endothelium, and to favor the growth of a confluent, stable monolayer of endothelial cells. This is accomplished here by combining electrospun poly(ethylene terephthalate) (PET) mats with an amine-rich thin plasma-polymerized coating, designated "L-PPE:N." Its deposition does not modify the open, highly porous mats and leads only to small changes in mechanical properties. L-PPE:N significantly improves the adhesion and growth of human umbilical vein endothelial cells (HUVEC) and their resistance to flow-induced shear stress. These properties favor the formation of desired confluent HUVEC monolayers on the topmost surface, unlike conventional vascular grafts (ePTFE or woven PET), where cells migrate inside the material. This combination is therefore highly advantageous for the pre-endothelialization of the luminal side of small-diameter vascular prostheses. PMID:24740559

Savoji, Houman; Hadjizadeh, Afra; Maire, Marion; Ajji, Abdellah; Wertheimer, Michael R; Lerouge, Sophie

2014-08-01

103

Stearyl methacrylate-grafted-chitosan nanoparticle as a nanofiller for PLA: Radiation-induced grafting and characterization  

NASA Astrophysics Data System (ADS)

This paper reports a one-pot synthesis using radiation-induced grafting technique to modify biopolymer-based chitosan nanoparticles as a nanofiller for blending with poly(lactic acid) (PLA). Hydrophobic stearyl methacrylate (SMA) was grafted onto non-irradiated chitosan (CS0) and pre-irradiated chitosan with a ?-ray dose of 40 kGy (CS40) to obtain stearyl methacrylate-grafted-chitosan nanoparticles (SMA-g-CSNPs).The effects of the pre-irradiated CS, grafting doses and SMA concentrations on degree of grafting (DG) and particle formation were studied. FT-IR and XRD were used to characterize the chemical and packing structure of SMA-g-CSNPs. The particle formulation and size of SMA-g-CSNPs were observed by TEM and AFM. The spherical core-shell SMA-g-CSNPs with the size ranging from 50 to 140 nm were successfully prepared. The SMA-g-CSNPs from CS40 has higher DG and smaller particle size when compared with CS0. The SMA-g-CSNPs are able to improve the compatibility between CS and PLA.

Rattanawongwiboon, Thitirat; Haema, Kamonwon; Pasanphan, Wanvimol

2014-01-01

104

Post radiation grafting of vinyl acetate onto low density polyethylene films: Preparation and properties of membrane  

NASA Astrophysics Data System (ADS)

Reverse osmosis membranes were prepared by the post radiation grafting of vinyl acetate onto low density polyethylene films. The factors affecting the grafting process such as radiation dose, monomer concentration and temperature on the grafting yield were studied. It was found that the dependence of the grafting rate on radiation intensity and monomer concentration was found to be of 0.64 and 1.4 order, respectively. The activation energy for this grafting system was calculated and found to be 4.45 kcal/mol above 30°C. Some properties of the grafted films such as specific electric resistance, water uptake, mechanical properties and thermal and chemical stability were investigated. An improvement in these properties was observed which makes possible the use of these membranes in some practical applications. The use of such membranes for reverse osmosis desalination of saline water was tested. The effect of operating time, degree of grafting and applied pressure on the water flux and salt rejection were determined. The results showed salt rejection percent over 90% and a reasonable water flux. A suitable degree of grafting of the membrane was determined as well as the optimum applied pressure.

M. Dessouki, Ahmed

105

Preparation of poly( N-isopropylacrylamide) brush grafted silica particles via surface-initiated atom transfer radical polymerization used for aqueous chromatography  

NASA Astrophysics Data System (ADS)

Thermoresponsive poly( N-isopropylacrylamide) (PNIPAAm) brushes were densely grafted onto silica surface via surface-initiated atom transfer radical polymerization (SI-ATRP). The grafting reaction started from the surfaces of 2-bromoisobutyratefunctionalized silica particles in 2-propanol aqueous solution at ambient temperature using CuCl/CuCl2/ N,N,N',N',N?-pentamethyldiethylenetriamine (PMDETA) as the catalytic system. Based on thermogravimetric analysis (TGA) results, the grafting amount and grafting density of PNIPAM chains on the surface of silica were calculated to be 1.29 mg/ m2 and 0.0215 chains/nm2, respectively. The gel permeation chromatography (GPC) result showed the relatively narrow molecular weight distribution ( M w/ M n= 1.21) of the grafted PNIPAAm. The modified silica particles were applied as high-performance liquid chromatography (HPLC) packing materials to successfully separate three aromatic compounds using water as mobile phase by changing column temperature. Temperature-dependent hydrophilic/hydrophobic property alteration of PNIPAAm brushes grafted on silica particles was determined with chromatographic interaction between stationary phase and analytes. Retention time was prolonged and resolution was improved with increasing temperature. Baseline separation with high resolution at relatively low temperatures was observed, demonstrating dense PNIPAAm brushes were grafted on silica surfaces.

Liu, Zong-Jian; Liang, Yan-Li; Geng, Fang-Fang; Lv, Fang; Dai, Rong-Ji; Zhang, Yu-Kui; Deng, Yu-Lin

2012-03-01

106

Kinetics of a methyl methacrylate polymerization initiated by the stable free radicals in irradiated polytetrafluoroethylene and properties of the resultant graft polymer  

SciTech Connect

The kinetics of the polymerization of methyl methacrylate (MMA) initiated by the stable free radicals in commercially available irradiated polytetrafluoroethylene micropowder and the rheological, thermal, chemical, and mechanical properties of the resultant graft polymer are described. Test tube runs using different ratios of MMA to PTFE were made to determine the feasibility of the reaction and optimum reaction conditions. The amount of graft produced was equal to the weight gain of the solids after removal of the adventitious homopolymer by extraction in acetone. Test quantities of material were produced in a 500 milliliter agitated reactor. A higher ratio of PTFE to excess MMA and longer reaction times result in higher conversion in test tubes. A kinetic model was developed to relate the original concentration of PTFE free radical to the amount of MMA polymer. Graft polymer containing PTFE micropowder, PMMA graft, and PMMA homopolymer in a ratio of 18:5:1 was used for property characterization. The graft material extrudes well at 513K and has a viscosity comparable to that of PMMA homopolymer. The material is stable upon re-extrusion. DSC thermograms show that the heat of transition of the PTFE melting peak is proportional to the amount of PTFE in the sample. Good solvents for PMMA are detrimental to the structural integrity of the graft extrudate; heat treatment improves the chemical resistance. The PTFE block controls the mechanical properties of the graft.

Donato, K.A.E.

1987-01-01

107

TEMPO addition into pre-irradiated fluoropolymers and living-radical graft polymerization of styrene for preparation of polymer electrolyte membranes  

NASA Astrophysics Data System (ADS)

We prepared proton exchange membranes (PEMs) by 2,2,6,6-tetramethylpiperidinyl-1-oxy (TEMPO)-mediated living-radical graft polymerization (LRGP) of styrene into fluoropolymer films and subsequent sulfonation. Poly(vinylidene fluoride) (PVDF) and poly(ethylene- co-tetrafluoroethylene) (ETFE) films were first irradiated and then treated with TEMPO solutions in various solvents. TEMPO addition was confirmed by the test of styrene grafting into TEMPO-treated films at 60 °C, at which the LRGP never proceeds. This test enabled us to differentiate the LRGP from the conventional graft polymerization. In order to gain a deep insight about TEMPO-addition reaction, the TEMPO-penetration behavior into the base polymer films was examined by a permeation experiment and computer simulation. Xylene and dioxane were appropriate solvents for the complete introduction of TEMPO into PVDF and ETFE films, respectively. Then, the LRGP of styrene was performed based on the fully TEMPO-capped films at 125 °C with various solvents. By using an alcoholic solvent, the degree of grafting was enhanced and it reached a maximum of 38%. This grafted film was sulfonated to prepare a PEM showing an ion exchange capacity of 2.2 meq/g and proton conductivity of 1.6×10 -1 S/cm.

Sawada, Shin-ichi; Suzuki, Akihiro; Terai, Takayuki; Maekawa, Yasunari

2010-04-01

108

Preparation of polysulfone nanofiltration membranes by UV-assisted grafting polymerization for water softening  

Microsoft Academic Search

The rising demand for high quality water heightens the need to soften hard and very hard water. In this study, flat sheet polysulfone ultrafiltration membranes were prepared by phase inversion and modified by UV-induced polymerization of acrylic acid in order to prepare nanofiltration membranes for water desalination. Polyethylene glycol of different molecular weights mainly in the range of 1500–4000Da were

Maryam Homayoonfal; Ahmad Akbari; Mohammad Reza Mehrnia

2010-01-01

109

Synthesis, modification and graft polymerization of magnetic nano particles for PAH removal in contaminated water  

PubMed Central

Magnetic nanoparticles (MNPs) were modified with 3-Mercaptopropytrimethoxysiline (MPTMS) and grafted with allyl glycidyl ether for coupling with beta naphtol as a method to form a novel nano-adsorbent to remove two poly aromatic hydrocarbons (PAHs) from contaminated water. The modified MNPs were characterized by transmission electron microscopy, infrared spectroscopy and thermogravimetric analysis. Results showed that the modified MNPs enhanced the process of adsorption. Tests were done on the adsorption capacity of the two PAHs on grafted MNPs; factors applied to the tests were temperature, contact time, pH, salinity and initial concentration of PAHs. Results revealed that adsorption equilibrium was achieved in 10 min, and the maximum adsorption capacity was determined as 4.15 mg/g at pH?=?7.0 and 20°C. The equilibrium adsorption data of the two PAHs by the modified MNPs were analyzed by Langmuir, Freundlich and Temkin models. Equilibrium adsorption data was determined from the Langmuir, Freundlich and Temkin constants from tests under conditions of pH?=?7 and temperature 20°C. Analysis of the adsorption-desorption process indicated that the modified MNPs had a high level of stability and good reusability. Magnetic separation in these tests was fast and this shows that the modified MNPs have great potential to be used as a new adsorbent for the two PAHs removal from contaminated water in water treatment. PMID:25101170

2014-01-01

110

Ion-containing reverse osmosis membranes obtained by radiation grafting method  

NASA Astrophysics Data System (ADS)

Cationic membranes obtained by radiation grafting of acqueous acrylic acid onto low density polyethylene films followed by alkaline treatment to confer ionic character in the graft chains, were tested for reverse osmosis desalination of saline water. Selected physical properties of such membranes were investigated. The grafted membranes prossess good mechanical and electrical properties. Water uptake for the alkali-treated membrane was much higher than that of the alkali-untreated one. The effect of operation time, degree of grafting, applied pressure and feed concentration on the water flux and salt rejection for the grafted membranes was investigated. Such cationic membranes showed good durability, thermal and chemical stability, acceptable water flux and salt rejection which may make them acceptable for practical use in reverse osmosis desalination of sea water.

Hegazy, El-Sayed A.; El-Assy, Nasef B.; Dessouki, Ahmed M.; Shaker, Manal M.

111

Analysis of a flexible polymeric film with imbedded micro heat pipes for spacecraft radiators  

E-print Network

radiators are being developed to accommodate deployment mechanisms. An analytical model suggests that a lightweight polymeric material with imbedded micro heat pipe arrays can meet heat dissipation requirements while contributing less mass than competing...

McDaniels, Deborah Marie

2001-01-01

112

Water diffusion within hydrated model grafted polymeric membranes with bimodal side chain length distributions.  

PubMed

The effect of bimodal side chain length distributions on pore morphology and solvent diffusion within hydrated amphiphilic polymeric membranes is predicted. Seven polymeric architectures are constructed from hydrophobic backbones from which at regular intervals side chains branch off that are alternatingly short (composed of p hydrophobic A fragments or beads) and long (q A fragments, q > p). The side chains are end-linked with a hydrophilic C fragment. Pore morphologies at a water volume fraction of 0.16 are calculated by dissipative particle dynamics (DPD). Water diffusion through the water containing pores is calculated by tracer diffusion calculations through 140 selected snapshots and from the water bead motions. Diffusion constants decrease with difference in side chain lengths, q - p. Overall, the distance between pores also decreases with q - p. The results are explained by counting for every architecture the average number of bonds ?Nbond? between an A and the nearest C fragment. These results are in line with a database that contains more than 60 architectures. Diffusion constants tend to increase linearly with ?Nbond?|C|(-1)|A|, where |C| and |A| are the C and A bead fractions within the architecture. ?Nbond? is therefore expected to be an interesting design parameter for obtaining low percolation thresholds for solvent and/or proton diffusion. PMID:25703230

Dorenbos, G

2015-03-25

113

New Applications of Ring-Opening Metathesis Polymerization for Grafting Alkylene Oxide-Based Copolymers  

NASA Astrophysics Data System (ADS)

This research tackles the challenges of innovative modification of poly(allyl alkylene oxides) by ROMP to produce new materials. Firstly, binary and ternary copolymers, poly(epichlorohydrin-allyl glycidyl ether) (ECH-AGE) and poly (epichlorohydrin-propylene oxide-allyl glycidyl ether) (ECH-PO-AGE), have been prepared using as initiator a catalytic system consisting of an alkyl aluminium, controlled amounts of water and different compounds (ethers, diols, phosphines, salicylic acid derivatives, organozincs) acting as cocatalysts. Among catalysts explored in these copolymerizations most productive showed to be the systems triisobutylaluminium (TIBA), water and Zn(DIPS)2 or Zn(acac)2. Copolymers which have become thus available were subsequently grafted onto the pendent allylic groups by ROMP with cycloolefins (cyclooctene, norbornene, cyclododecene) involving ruthenium based catalysts.

Spurcaciu, Bogdan; Buzdugan, Emil; Nicolae, Cristian; Ghioca, Paul; Iancu, Lorena; Dragutan, Valerian; Dragutan, Ileana

114

An efficient approach to obtaining water-compatible and stimuli-responsive molecularly imprinted polymers by the facile surface-grafting of functional polymer brushes via RAFT polymerization.  

PubMed

A new and efficient approach to obtaining molecularly imprinted polymers (MIPs) with both pure water-compatible (i.e., applicable in the pure aqueous environments) and stimuli-responsive binding properties is described, whose proof-of-principle is demonstrated by the facile modification of the preformed MIP microspheres via surface-initiated reversible addition-fragmentation chain transfer (RAFT) polymerization of N-isopropylacrylamide (NIPAAm). The presence of poly(NIPAAm) (PNIPAAm) brushes on the obtained MIP microspheres was confirmed by FT-IR as well as the water dispersion and static contact angle experiments, and some quantitative information including the molecular weights and polydispersities of the grafted polymer brushes, the thickness of the polymer brush layers, and their grafting densities was provided. In addition, the binding properties of the ungrafted and grafted MIPs/NIPs in both methanol/water (4/1, v/v) and pure water solutions were also investigated. The introduction of PNIPAAm brushes onto the MIP microspheres has proven to significantly improve their surface hydrophilicity and impart stimuli-responsive properties to them, leading to their pure water-compatible and thermo-responsive binding properties. The application of the facile surface-grafting approach, together with the versatility of RAFT polymerization and the availability of many different functional monomers, makes the present methodology a general and promising way to prepare water-compatible and stimuli-responsive MIPs for a wide range of templates. PMID:20837394

Pan, Guoqing; Zhang, Ying; Guo, Xianzhi; Li, Chenxi; Zhang, Huiqi

2010-11-15

115

[A comparative study of ethylene oxide and ionizing radiation for sterilizing bone grafts].  

PubMed

To find a good way for sterilization and disinfection of bone grafts, we compared the sterilization capacity of gaseous ethylene oxide (EO) and cobalt-60 gamma radiation. The bone chips were contaminated with 10(7) bacteria per milliliter of Staphylococcus aureus ATCC 25923, Bacillus subtilis globigii 8017 and Bacillus cereus 4001, then sterilized with various doses of gaseous EO or cobalt- 60 gamma radiation. The sterilization effect of EO was more stronger and faster than that of 60Co gamma radiation. The application of moderate doses of EO for sterilizing particulate bone grafts was recommended. PMID:9594188

Sang, H; Hu, Y; Sun, Y

1996-08-01

116

Study on poly-electrolyte membrane of crosslinked PTFE by radiation-grafting  

Microsoft Academic Search

Polymer electrolyte fuel cell membrane based on crosslinked polytetrafluoroethylene (PTFE) [RX-PTFE] has been processed by radiation-grafting with reactive styrene monomers by ?-rays under atmospheric circumstances, and the characteristic properties of the obtained membranes have been studied. The grafting yields of styrene monomer onto RX-PTFE, which have various crosslinking densities, were in the range of 5–100%. At the reaction period of

Kohei Sato; Shigetoshi Ikeda; Minoru Iida; Akihiro Oshima; Yoneho Tabata; Masakazu Washio

2003-01-01

117

Modification of fiber properties through grafting of acrylonitrile to rayon by chemical and radiation methods  

PubMed Central

Fibrous properties of rayon has been modified through synthesis of graft copolymers of rayon with acrylonitrile (AN) by chemical method using ceric ammonium nitrate (CAN/HNO3) as a redox initiator and gamma radiation mutual method. Percentage of grafting (Pg) was determined as a function of initiator concentration, monomer concentration, irradiation dose, temperature, time of reaction and the amount of water. Maximum percentage of grafting (160.01%) using CAN/HNO3 was obtained at [CAN] = 22.80 × 10?3 mol/L, [HNO3] = 112.68 × 10?2 mol/L and [AN] = 114.49 × 10?2 mol/L in 20 mL of water at 45 °C within 120 min while in case of gamma radiation method, maximum Pg (90.24%) was obtained at an optimum concentration of AN of 76.32 × 10?2 mol/L using 10 mL of water at room temperature with total dose exposure of 3.456 kGy/h. The grafted fiber was characterized by FTIR, SEM, TGA and XRD studies. Swelling behavior of grafted rayon in different solvents such as water, methanol, ethanol, DMF and acetone was studied and compared with the unmodified rayon. Dyeing behavior of the grafted fiber was also investigated. PMID:25685464

Kaur, Inderjeet; Sharma, Neelam; Kumari, Vandna

2013-01-01

118

Modification of fiber properties through grafting of acrylonitrile to rayon by chemical and radiation methods.  

PubMed

Fibrous properties of rayon has been modified through synthesis of graft copolymers of rayon with acrylonitrile (AN) by chemical method using ceric ammonium nitrate (CAN/HNO3) as a redox initiator and gamma radiation mutual method. Percentage of grafting (Pg) was determined as a function of initiator concentration, monomer concentration, irradiation dose, temperature, time of reaction and the amount of water. Maximum percentage of grafting (160.01%) using CAN/HNO3 was obtained at [CAN] = 22.80 × 10(-3) mol/L, [HNO3] = 112.68 × 10(-2) mol/L and [AN] = 114.49 × 10(-2) mol/L in 20 mL of water at 45 °C within 120 min while in case of gamma radiation method, maximum Pg (90.24%) was obtained at an optimum concentration of AN of 76.32 × 10(-2) mol/L using 10 mL of water at room temperature with total dose exposure of 3.456 kGy/h. The grafted fiber was characterized by FTIR, SEM, TGA and XRD studies. Swelling behavior of grafted rayon in different solvents such as water, methanol, ethanol, DMF and acetone was studied and compared with the unmodified rayon. Dyeing behavior of the grafted fiber was also investigated. PMID:25685464

Kaur, Inderjeet; Sharma, Neelam; Kumari, Vandna

2013-11-01

119

Stability of SG1 nitroxide towards unprotected sugar and lithium salts: a preamble to cellulose modification by nitroxide-mediated graft polymerization  

PubMed Central

Summary The range of applications of cellulose, a glucose-based polysaccharide, is limited by its inherently poor mechanical properties. The grafting of synthetic polymer chains by, for example, a “grafting from” process may provide the means to broaden the range of applications. The nitroxide-mediated polymerization (NMP) method is a technique of choice to control the length, the composition and the architecture of the grafted copolymers. Nevertheless, cellulose is difficult to solubilize in organic media because of inter- and intramolecular hydrogen bonds. One possibility to circumvent this limitation is to solubilize cellulose in N,N-dimethylformamide (DMF) or N,N-dimethylacetamide (DMA) with 5 to 10 wt % of lithium salts (LiCl or LiBr), and carry out grafted polymerization in this medium. The stability of nitroxides such as SG1 has not been studied under these conditions yet, even though these parameters are of crucial importance to perform the graft modification of polysaccharide by NMP. The aim of this work is to offer a model study of the stability of the SG1 nitroxide in organic media in the presence of unprotected glucose or cellobiose (used as a model of cellulose) and in the presence of lithium salts (LiBr or LiCl) in DMF or DMA. Contrary to TEMPO, SG1 proved to be stable in the presence of unprotected sugar, even with an excess of 100 molar equivalents of glucose. On the other hand, lithium salts in DMF or DMA clearly degrade SG1 nitroxide as proven by electron-spin resonance measurements. The instability of SG1 in these lithium-containing solvents may be explained by the acidification of the medium by the hydrolysis of DMA in the presence of LiCl. This, in turn, enables the disproportionation of the SG1 nitroxide into an unstable hydroxylamine and an oxoammonium ion. Once the conditions to perform an SG1-based nitroxide-mediated graft polymerization from cellobiose have been established, the next stage of this work will be the modification of cellulose and cellulose derivatives by NMP. PMID:23946859

Moreira, Guillaume; Charles, Laurence; Major, Mohamed; Vacandio, Florence; Guillaneuf, Yohann

2013-01-01

120

Radiation-grafting of thermo- and pH-responsive poly(N-vinylcaprolactam-co-acrylic acid) onto silicone rubber and polypropylene films for biomedical purposes  

NASA Astrophysics Data System (ADS)

This work focuses on the effects of gamma-ray irradiation conditions on the stimuli-responsiveness of polypropylene (PP) films and silicone (SR) rubber substrates grafted with N-vinylcaprolactam (NVCL) and acrylic acid (AAc). PP films and SR rubber were modified by simultaneous polymerization and grafting of NVCL and AAc, using pre-irradiation oxidative method at a dose rate of 12.23 kGy h-1 and doses ranging from 5 to 70 kGy. NVCL and AAc solutions (1/1, v/v) at 50% monomer concentration (v/v) in toluene were added to the sample substrates, degassed, sealed and heated at 60 and 70 °C for 12 h. After grafting, the samples were soaked in ethanol and distilled water for 24 h successively, followed by drying under vacuum. Samples were characterized by FTIR-ATR, DSC and swelling measurements. Critical points (pH critical or LCST) of grafts were obtained in a pH-environment (pH ranges from 2.2 to 9) and in a thermo-environment (temperature ranges from 22 to 50 °C). Cytotoxicity evaluation was performed using fibroblast BALB/c 3T3 cells. The relationship between NVCL-co-AAc grafting and radiation dose was different for each substrate, PP and SR. At 50% NVCL/AAc concentration in toluene, grafting values were higher for SR than for PP. Despite the fact that PP-g-(NVCL-co-AAc) membrane presented a cytotoxic profile at the highest experimental concentration assayed, cytotoxicity evaluation revealed noncytotoxic profiles for the membranes synthesized highlighting their applications for biomedical purposes.

Ferraz, Caroline C.; Varca, Gustavo H. C.; Ruiz, Juan-Carlos; Lopes, Patricia S.; Mathor, Monica B.; Lugăo, Ademar B.; Bucio, Emilio

2014-04-01

121

Evaluation of graft stiffness using acoustic radiation force impulse imaging after living donor liver transplantation.  

PubMed

Acoustic radiation force impulse (ARFI) imaging is an ultrasound-based modality to evaluate tissue stiffness using short-duration acoustic pulses in the region of interest. Virtual touch tissue quantification (VTTQ), which is an implementation of ARFI, allows quantitative assessment of tissue stiffness. Twenty recipients who underwent living donor liver transplantation (LDLT) for chronic liver diseases were enrolled. Graft types included left lobes with the middle hepatic vein and caudate lobes (n = 11), right lobes (n = 7), and right posterior segments (n = 2). They underwent measurement of graft VTTQ during the early post-LDLT period. The VTTQ value level rose after LDLT, reaching a maximum level on postoperative day 4. There were no significant differences in the VTTQ values between the left and right lobe graft types. Significant correlations were observed between the postoperative maximum value of VTTQ and graft volume-to-recipient standard liver volume ratio, portal venous flow to graft volume ratio, and post-LDLT portal venous pressure. The postoperative maximum serum alanine aminotransferase level and ascites fluid production were also significantly correlated with VTTQ. ARFI may be a useful diagnostic tool for the noninvasive and quantitative evaluation of the severity of graft dysfunction after LDLT. PMID:25203425

Ijichi, Hideki; Shirabe, Ken; Matsumoto, Yoshihiro; Yoshizumi, Tomoharu; Ikegami, Toru; Kayashima, Hiroto; Morita, Kazutoyo; Toshima, Takeo; Mano, Yohei; Maehara, Yoshihiko

2014-11-01

122

Hemocompatibility and anti-biofouling property improvement of poly(ethylene terephthalate) via self-polymerization of dopamine and covalent graft of zwitterionic cysteine.  

PubMed

Inspired by the composition of adhesive proteins in mussels, we used self-polymerized dopamine to form a thin and surface-adherent polydopamine layer onto poly(ethylene terephthalate) (PET) sheet, followed by covalent grafting cysteine (Cys) to improve hemocompatibility and anti-biofouling property. The obtained surfaces were characterized by water contact angle measurements (WCA), attenuated total reflectance Fourier transform infrared spectroscopy (ATR-FTIR), and X-ray photoelectron spectroscopy (XPS) analysis. The results of platelet adhesion and protein adsorption tests showed that cysteine immobilized PET was endowed with improved resistance to nonspecific protein adsorption and platelet adhesion. The results of hemolysis rate test showed cysteine grafted PET (PET-g-Cys) had low hemolytic ability. Cell assay results showed that PET-g-Cys surface could greatly inhibit HeLa cell adhesion. These works provide an ideal hemocompatible and antifouling surface for biomedical applications. PMID:23735748

Li, Pengfei; Cai, Xianmei; Wang, Ding; Chen, Shuangchun; Yuan, Jiang; Li, Li; Shen, Jian

2013-10-01

123

Polymers from renewable resources: kinetics of 4-vinyl pyridine radiochemical grafting onto cellulose extracted from pine needles  

NASA Astrophysics Data System (ADS)

In view of the marked thrust of research activities in the area of biodegradable polymers use of pine needles as renewable stock of polymeric materials has been made to synthesize graft copolymers for biomedical and industrial applications. 4-Vinyl pyridine (4-VP) has been radiochemically grafted onto cellulose extracted from pine needles using simultaneous irradiation method in limited aqueous medium. Optimum grafting conditions and kinetic parameters such as percent grafting, grafting efficiency, total conversion of monomer and rates of polymerization, homopolymerization and grafting have been evaluated as a function of total dose, monomer concentration and amount of water. It is observed that variation in both total dose and monomer concentration leads to inconsistent increase and decrease of the grafting parameters. However, rate of polymerization shows unsteady but regular increase with increasing monomer concentration and total dose radiation. While optimum amount of water is required for maximum percent grafting, addition of methanol on the other hand leads to regular decrease in percent grafting as a consequence of fall in the rate of grafting contrary to some earlier reported studies. Evidence of grafting has been based on the comparative studies of cellulose and grafted cellulose by infrared spectroscopy, elemental analysis and thermal analysis. Grafting enhances thermal stability of cellulose backbone. The trends in the results have been explained by kinetic interpretation and suitable mechanism for grafting has been proposed.

Chauhan, Ghanshyam S.; Dhiman, Surya K.; Guleria, Lalit K.; Misra, Bhupendra N.; Kaur, Inderjeet

2000-04-01

124

Role of additives in wood polymer composites. Relationship to analogous radiation grafting and curing processes  

NASA Astrophysics Data System (ADS)

Wood polymer composites (WPC) were prepared by impregnating an Australian softwood, Pinus radiata with methyl methacrylate which subsequently underwent in situ polymerisation utilising either ? radiation or the catalyst-accelerator method. Novel additives including thermal initiator, crosslinking agents, an inclusion compound and oxygen scavenger were incorporated to improve the polymer loading and properties of the resulting WPC. Polymer loadings of WPC obtained utilising the accelerator-catalyst method corresponded well with those obtained using ? radiation with 20 kGy radiation dose. The mechanistic significance of the current work in analogous radiation grafting and curing processes is discussed.

Ng, Loo-Teck; Garnett, John L.; Mohajerani, Shahroo

1999-08-01

125

Current status of adsorbent for metal ions with radiation grafting and crosslinking techniques  

NASA Astrophysics Data System (ADS)

Removal of toxic metals from streaming water and ground water is important task to preserve environment. Radiation processing of grafting and crosslinking can synthesis adsorbent having high performances. Graft adsorbent can be synthesized by using the conventional polymer like polyethylene having variety shapes such as membrane, cloth, and fiber. Especially, the obtained fibrous adsorbent has 100 times higher rate of adsorption than that of commercialized resin. Fibrous adsorbent of iminodiacetate was applied to the removal of cadmium from the scallop waste. Furthermore, the amidoxime adsorbent is useful for recovery of rare metals such as uranium and vanadium in seawater. Novel fibrous adsorption for arsenic was synthesized by direct grafting of phosphoric monomer and following zirconium-loading. Crosslinked natural polymers like carboxymethyl chitin-chitosan in the paste-like state are applicable for the metal adsorbent. This adsorbent can be biodegraded after usage.

Seko, Noriaki; Tamada, Masao; Yoshii, Fumio

2005-07-01

126

Morphological characterization of a polymeric microfiltration membrane by synchrotron radiation computed microtomography  

E-print Network

to characterize the 3D structure of a PvDF hollow fibre microfiltration membrane prepared by phase inversion. 3D1 Morphological characterization of a polymeric microfiltration membrane by synchrotron radiation membranes are prepared by phase inversion. The performance of the membranes depends greatly

Paris-Sud XI, UniversitĂŠ de

127

Laser radiation in the treatment of prosthetic graft stenosis. A preliminary study of prosthesis damage by laser energy  

SciTech Connect

Transluminal laser recanalization is potentially an important new treatment of anastomotic intimal hyperplasia. However, currently used grafts or sutures may be damaged by laser radiation at power and energy levels required for plaque removal. To investigate this problem, two commonly used grafts (Dacron and polytetrafluoroethylene (PTFE)) and two types of vascular suture (polypropylene and PTFE) were exposed to argon laser radiation in vitro. Dacron and PTFE grafts recovered from amputations were also studied to determine whether graft healing affected graft resistance to laser damage. Power and energy levels required to perforate atherosclerotic superficial femoral arteries were determined for comparison. PTFE grafts were significantly (1.5 to 7 times) more resistant to perforation by laser energy than atherosclerotic arteries under all conditions. In contrast, Dacron grafts perforated at power and energy levels one half to one third of that required for vaporization of atherosclerotic plaque. PTFE sutures remained intact at power and energy levels above the levels that perforated atherosclerotic arteries, whereas polypropylene sutures were destroyed by very low levels of power and energy (0.5 joules at 0.5 watts). Because of the variable levels of power and energy that damage different types of prosthetic grafts and sutures, laser angioplasty should only be investigated clinically as a therapy for anastomotic intimal hyperplasia when PTFE grafts and sutures are present.

Seeger, J.M.; Abela, G.S.; Klingman, N.

1987-09-01

128

Studies on the immobilization of biofunctional components by radiation polymerization and their applications  

NASA Astrophysics Data System (ADS)

The recent progress on the studies of immobilization of various biofunctional components mainly by mean of radiation polymerization as well as their practical applications to biomedical and biochemical fields were reviewed. The immobilization of drugs for the controlled release and targetting, the immobilization of antigens and antibodies for the immunodiagnosis, and the immobilization of microorganisms and tissue cells for the cell culture and the biomass conversion were the main topics in this review. The new findings on the enhanced immobilization methods and the polymeric carriers for immobilization were also attached.

Kaetsu, Isao; Kumakura, Minoru; Fujimura, Takashi; Yoshida, Masaru; Asano, Masaharu; Kasai, Noboru; Tamada, Masao

129

Preparation and characterization of a magneto-polymeric nanocomposite: Fe 3O 4 nanoparticles in a grafted, cross-linked and plasticized poly(vinyl chloride) matrix  

NASA Astrophysics Data System (ADS)

In this work two kind of materials: (1) grafted, cross-linked and plasticized poly(vinyl chloride) (PVC) "plastic films" and (2) magnetic plastic films "magneto-polymeric nanocomposites" were prepared. Precursor solutions or "plastisols" used to obtain the plastic films were obtained by mixing PVC (emulsion grade) as polymeric matrix, di(2-ethylhexyl)phthalate (DOP) as plasticizer, a thermal stabilizer based in Ca/Zn salts, and a cross-linking agent, 3-mercaptopropyltrimethoxysilane (MTMS) or 3-aminopropyltriethoxysilane (ATES), at several concentrations. Flexible films were obtained from the plastisols using static casting. The stress-strain behavior and the gel content (determined by Soxhlet extraction with boiling THF) of the flexible films were measured in order to evaluate the effect of the cross-linking agent and their content on the degree of cross-linking. The magneto-polymeric nanocomposites were obtained by mixing the optimum composition of the plastisols (analyzed previously) with magnetite (Fe 3O 4)-based ferrofluid and DOP. Later, flexible films were obtained by static casting of the plastisol/ferrofluid systems. The magnetic films were characterized by the above-mentioned techniques and X-ray diffraction, vibrating sample magnetometry and thermogravimetrical analysis.

Rodríguez-Fernández, Oliverio S.; Rodríguez-Calzadíaz, C. A.; Yáńez-Flores, Isaura G.; Montemayor, Sagrario M.

130

On the mechanism of radiation-induced polymerization of vinyl monomers in ionic liquid  

NASA Astrophysics Data System (ADS)

An attempt was made to investigate the mechanism controlling the radiation-induced polymerization of vinyl monomers in room temperature ionic liquids. For that purpose, copolymerization of styrene (St) and methyl methacrylate (MMA) was initiated by 60Co gamma radiation in a moisture-stable ionic liquid, [choline chloride][ZnCl 2], and its mixture with THF (4:1 v/v). By analyzing the product composition with FTIR for a series of poly(St-co-MMA) samples, it was found that the mole fraction of St in the copolymer is linearly proportional to the mole fraction of St in the feed. Therefore, radiation polymerization in ionic liquid and its mixture with organic solvent is suggested to be a radical propagating process.

Liu, Yaodong; Wu, Guozhong

2005-06-01

131

Fabrication of PEFC membrane based on PTFE\\/FEP polymer-alloy using radiation-grafting  

Microsoft Academic Search

Polymer electrolyte fuel cells (PEFC) membranes based on very thin film of network polytetrafluoroethylene (PTFE)\\/tetrafluoroethylene-co-hexafluoropropylene (FEP) polymer-alloy (PTFE\\/FEP polymer-alloy: FE), have been fabricated by radiation-grafting with reactive styrene monomers using electron beam irradiation (EB) under nitrogen atmosphere at room temperature. The characteristic properties of obtained materials have been measured by ion exchange capacity (IEC), Fourier transform infrared spectroscopy (FT-IR), differential

Saneto Asano; Fumihiro Mutou; Shogo Ichizuri; Jingye Li; Takaharu Miura; Akihiro Oshima; Yosuke Katsumura; Masakazu Washio

2005-01-01

132

Influence of matrix porosity on the immobilization of penicillin acylase by radiation-induced polymerization  

NASA Astrophysics Data System (ADS)

Penicillin acylase was immobilized by low temperature radiation-induced polymerization into polymer matrices obtained from monomers of different hydrophilicities, at various ratios of monomer to enzyme solution and at different polymerization conversions. It was found that the penicillin acylase retention (60-85% of the starting enzyme) is independent of the monomer used in thepolymerization, of the polymerization conversion and of the porosity of the polymer matrix. On the other hand, the penicillin acylase retention strongly depends on the presence in the irradiation mixture of the hydrophobic crosslinking agent, trimethylolpropane trimethacrylate, even in low amounts. The data suggest that the enzyme is bound to the polymer matrix by hydrophobic interactions through crosslinking agent molecules.

Carenza, M.; Lora, S.; Palma, G.; Bocců, E.; Largajolli, R.; Veronese, F. M.

133

Time resolved study of the high energy radiation initiated polymerization  

NASA Astrophysics Data System (ADS)

The EB (electron beam) initiated polymerization of ethyl acrylate (EA) and ethyl methacrylate (EMA) in dilute cyclohexane solution was studied by pulse radiolysis technique with transient spectroscopic detection. The maximum in the absorption spectrum of the intermediates lies at ? = 290-320 nm in EA solution and at ? = 285 in EMA solution. The extinction coefficients of the intermediates at the maximum of the spectrum were calculated to be ?285nm ˜ 700 mol -1 dm 3 cm -1 in EMA solution and ?290-320nm ˜ 300 mol -1 dm 3 cm -1 in EA solution. From the decay curves rate parameters of termination (2 kt) were calculated. The decays were generally found to be second order with a rate coefficient of 1.4 × 10 9mol -1 dm 3 s -1 in EMA solutions and 6 × 10 8mol -1 dm 3 s -1 in EA solutions. In some cases deviation from a single second order was observed. This was interpreted in terms of the hindered mobility of the growing radicals.

Takács, E.; Wojnárovits, L.

1995-11-01

134

Fabrication of PEFC membrane based on PTFE/FEP polymer-alloy using radiation-grafting  

NASA Astrophysics Data System (ADS)

Polymer electrolyte fuel cells (PEFC) membranes based on very thin film of network polytetrafluoroethylene (PTFE)/tetrafluoroethylene-co-hexafluoropropylene (FEP) polymer-alloy (PTFE/FEP polymer-alloy: FE), have been fabricated by radiation-grafting with reactive styrene monomers using electron beam irradiation (EB) under nitrogen atmosphere at room temperature. The characteristic properties of obtained materials have been measured by ion exchange capacity (IEC), Fourier transform infrared spectroscopy (FT-IR), differential scanning calorimetry (DSC), and so on. The grafting yields showed the initial rapid increase, and then tended to saturate above 5-8 h. The grafting yields of all FE with various network densities have been achieved 80-100%. The styrene-grafted materials were sulfonated by chlorosulfonic acid. The IECs of sulfonated materials based on FE polymer-alloy have been achieved 3.0 meq/g. This suggests that IEC value is independent on network density and PTFE/FEP blend ratio. The IEC values of obtained materials are about three times higher than those of commercial perfluoro-sulfonic acid (PFSA) membranes. By small angle X-ray scattering (SAXS), it is found that the higher network densities would give the smaller cluster sizes in sulfonated materials. Thus, the higher amount of FEP will give the smaller cluster formation of sulfonated materials.

Asano, Saneto; Mutou, Fumihiro; Ichizuri, Shogo; Li, Jingye; Miura, Takaharu; Oshima, Akihiro; Katsumura, Yosuke; Washio, Masakazu

2005-07-01

135

The effect of vacuum freeze-drying and radiation on allogeneic aorta grafts.  

PubMed

Vacuum freeze-dried aorta is a satisfactory material for blood vessel grafting. Previous studies have focused on immunity, however, vacuum freeze-drying is a complicated process of heat and mass transfer, and adopting a programmed cooling process may more completely preserve the mechanical properties of the blood vessels. Irradiation, as a method of removing pathogens, lowers the antigenic activity of the blood vessels. In our study, vacuum freeze-drying combined with radiation was used as a treatment for porcine aorta prior to grafting, aimed at deactivating endogenous retrovirus, shielding masses of endothelial cells and lowering the immunogenicity of the blood vessels. As for the mechanical properties, compared with normal aorta, the maximum axial tensile stress (ATS) decreased by 20%, the maximum circumferential tensile stress (CTS) increased by 30% and the maximum puncture stress (PT) decreased by 20%. Our results revealed that 2 months after of grafting, the host cells had migrated into the graft tissue and propagated to initiate endothelialization, the inflammatory reaction was abated and the PT had returned to normal levels. PMID:23128779

Cao, Qing; Tao, Leren; Liu, Mengfang; Yin, Meng; Sun, Kun

2013-01-01

136

Comparative study of grafting a polyampholyte in a fluoropolymer membrane by gamma radiation in one or two-steps  

NASA Astrophysics Data System (ADS)

Binary graft copolymerization of pH-sensitive monomers (N,N-dimethylaminoethyl methacrylate, (DMAEMA) and acrylic acid (AAc) onto polyvinylidene fluoride (PVDF) membranes with pore sizes of 0.22 and 0.45 ?m was conducted by one and two-steps grafting using a 60Co gamma radiation source (Gammabeam 651 PT). The DMAEMA and AAc monomers were grafted by an oxidative pre-irradiation method in one-step grafting to obtain PDVF-g-(DMAEMA-co-AAc), and both direct irradiation and an oxidative pre-irradiation method were used to obtain the graft copolymer (PVDF-g-DMAEMA)-g-AAc in two-steps grafting. The optimal conditions, such as reaction time, temperature, solvent, monomer concentration and dose, were studied, the aim of this work was to investigate how these factors affecting the graft percent of DMAEMA and AAc prepared in one and two-steps grafting and their structural differences and also characterize the grafting membrane through analytical techniques.

Estrada-Villegas, G. M.; Bucio, E.

2013-11-01

137

Hemocompatibility and anti-biofouling property improvement of poly(ethylene terephthalate) via self-polymerization of dopamine and covalent graft of lysine.  

PubMed

Inspired by the composition of adhesive proteins in mussels, we used self-polymerized dopamine to form a thin and surface-adherent polydopamine layer onto poly(ethylene terephthalate) (PET) sheet, followed by covalently grafting lysine (Lys) to improve hemocompatibility and anti-biofouling property. The obtained surfaces were characterized by water contact angle measurements, attenuated total reflectance Fourier transform infrared spectroscopy, and X-ray photoelectron spectroscopy analysis. The results of platelet adhesion and protein adsorption tests showed that Lys-immobilized PET was endowed with improved resistance to nonspecific protein adsorption and platelet adhesion. Cell assay results showed that PET-g-Lys surface could greatly inhibit NIH 3T3 cell adhesion. These works provide a facile hemocompatible and anti-fouling surface for biomedical applications. PMID:25075613

Zhi, Xuelian; Li, Pengfei; Gan, Xucheng; Zhang, Weiwei; Shen, Tianjiao; Yuan, Jiang; Shen, Jian

2014-01-01

138

Poly(2-hydroxyethyl methacrylate) grafted halloysite nanotubes as a molecular host matrix for luminescent ions prepared by surface-initiated RAFT polymerization and coordination chemistry  

NASA Astrophysics Data System (ADS)

A fluorescent nanohybrid complex comprising of halloysite nanotubes (HNTs), poly(2-hydroxyethyl methacrylate) (PHEMA), and europium ions (Eu3+) was synthesized by the combination of surface-initiated reversible addition-fragmentation chain transfer (SI-RAFT) polymerization and coordination chemistry. Initially, PHEMA was grafted from the HNTs by SI-RAFT and then reacted with succinic anhydride to provide carboxyl acid groups on the external layers of HNTs-g-PHEMA nanohybrids. The subsequent coordination of the nanohybrids with Eu3+ ions afforded photoluminescent Eu3+ tagged HNTs-g-PHEMA nanohybrid complexes (HNTs-g-PHEMA-Eu3+). The structure, morphology, and fluorescence properties of the Eu3+ coordinated nanohybrid complexes were investigated by respective physical and spectral studies. FT-IR, XPS, and EDS analyses suggested the formation of the HNTs-g-PHEMA-Eu3+ nanohybrids. FE-SEM images indicated the immobilization of polymer layers on HNTs. TGA scans further demonstrated the grafting of PHEMA onto HNTs surface. The optical properties of HNTs-g-PHEMA-Eu3+ nanohybrid complexes were investigated by photoluminescence spectroscopy.

Islam, Md. Rafiqul; Bach, Long Giang; Lim, Kwon Taek

2013-07-01

139

Grafting of Poly(methyl methacrylate) Brushes from Magnetite Nanoparticles Using a Phosphonic Acid Based Initiator by Ambient Temperature Atom Transfer Radical Polymerization (ATATRP)  

NASA Astrophysics Data System (ADS)

Poly(methyl methacrylate) in the brush form is grown from the surface of magnetite nanoparticles by ambient temperature atom transfer radical polymerization (ATATRP) using a phosphonic acid based initiator. The surface initiator was prepared by the reaction of ethylene glycol with 2-bromoisobutyrl bromide, followed by the reaction with phosphorus oxychloride and hydrolysis. This initiator is anchored to magnetite nanoparticles via physisorption. The ATATRP of methyl methacrylate was carried out in the presence of CuBr/PMDETA complex, without a sacrificial initiator, and the grafting density is found to be as high as 0.90 molecules/nm2. The organic inorganic hybrid material thus prepared shows exceptional stability in organic solvents unlike unfunctionalized magnetite nanoparticles which tend to flocculate. The polymer brushes of various number average molecular weights were prepared and the molecular weight was determined using size exclusion chromatography, after degrafting the polymer from the magnetite core. Thermogravimetric analysis, X-ray photoelectron spectra and diffused reflection FT-IR were used to confirm the grafting reaction.

Babu, Kothandapani; Dhamodharan, Raghavachari

2008-03-01

140

Role of polymeric endosomolytic agents in gene transfection: a comparative study of poly(L-lysine) grafted with monomeric L-histidine analogue and poly(L-histidine).  

PubMed

Endosomal entrapment is one of the main barriers that must be overcome for efficient gene expression along with cell internalization, DNA release, and nuclear import. Introducing pH-sensitive ionizable groups into the polycationic polymers to increase gene transfer efficiency has proven to be a useful method; however, a comparative study of introducing equal numbers of ionizable groups in both polymer and monomer forms, has not been reported. In this study, we prepared two types of histidine-grafted poly(L-lysine) (PLL), a stacking form of poly(L-histidine) (PLL-g-PHis) and a mono-L-histidine (PLL-g-mHis) with the same number of imidazole groups. These two types of histidine-grafted PLL, PLL-g-PHis and PLL-g-mHis, showed profound differences in hemolytic activity, cellular uptake, internalization, and transfection efficiency. Cy3-labeled PLL-g-PHis showed strong fluorescence in the nucleus after internalization, and high hemolytic activity upon pH changes was also observed from PLL-g-PHis. The arrangement of imidazole groups from PHis also provided higher gene expression than mHis due to its ability to escape the endosome. mHis or PHis grafting reduced the cytotoxicity of PLL and changed the rate of cellular uptake by changing the quantity of free ?-amines available for gene condensation. The subcellular localization of PLL-g-PHis/pDNA measured by YOYO1-pDNA intensity was highest inside the nucleus, while the lysotracker, which stains the acidic compartments was lowest among these polymers. Thus, the polymeric histidine arrangement demonstrate the ability to escape the endosome and trigger rapid release of polyplexes into the cytosol, resulting in a greater amount of pDNA available for translocation to the nucleus and enhanced gene expression. PMID:25144273

Hwang, Hee Sook; Hu, Jun; Na, Kun; Bae, You Han

2014-10-13

141

Radiation induced graft copolymerization of n-butyl acrylate onto poly(ethylene terephthalate) (PET) films and thermal properties of the obtained graft copolymer  

NASA Astrophysics Data System (ADS)

n-Butyl acrylate (BA) was successfully grafted onto poly(ethylene terephthalate) (PET) film using simultaneous radiation induced graft copolymerization with gamma rays. When BA concentration ranges from 20% to 30%, the Degree of Grafting (DG), measured by gravimetry and 1H NMR, increases with the monomer concentration and absorbed dose, but decreases with dose rate from 0.83 to 2.53 kGy/h. The maximum DG can reach up to 22.1%. The thermal transition temperatures such as glass-transition temperature ( Tg) and cold-crystallization temperature ( Tcc) of PET in grafted films were little different from those in original PET film, indicating that microphase separation occurred between PBA side chains and PET backbone. This work implied that if PET/elastomers (e.g., acrylate rubber) blends are radiated by high energy gamma rays under a certain condition, PET-g-polyacrylate copolymer may be produced in-situ, which will improve the compatibility between PET and the elastomers so as to improve the integral mechanical properties of PET based engineering plastic.

Ping, Xiang; Wang, Mozhen; Ge, Xuewu

2011-05-01

142

Preparation, structure and properties of metal–copolymer complexes of poly-4-vinylpyridine radiation-grafted onto polymer films  

Microsoft Academic Search

Copolymer products were prepared by radiation grafting of 4-vinylpyridine onto films of low-density poly(ethylene) and poly(tetrafluoroethylene) (PE-graft-P4VP and PTFE-graft-P4VP, respectively). The corresponding metal complexes were in turn obtained by interaction of the radiation-grafted copolymers with aqueous solutions of various salts such as FeCl3ˇ6H2O, CoCl2ˇ6H2O, VOSO4ˇ5H2O, Na2MoO4ˇ2H2O and Na2WO4ˇ2H2? at room temperature. The content of metal ions was found to be

Sevdalina Turmanova; Krassimir Vassilev; Stanka Boneva

2008-01-01

143

Cell Fouling Resistance of Polymer Brushes Grafted from Ti Substrates by Surface-Initiated Polymerization: Effect of  

E-print Network

) (PEG),4,5 formation of self-assembled monolayers (SAMs),6 monolayer/ multilayer polyelectrolyte(oligo(ethylene glycol) methyl ether methacrylate) (POEGMEMA) polymer thin films of approximate 100 nm thickness were and photochemical attachment of polymer thin films.9 Recently, the technique of surface-initiated polymerization

144

Radiation-induced graft copolymerization of styrene with vinylic monomers at high dose rates  

NASA Astrophysics Data System (ADS)

Radiation-induced graft copolymerization of the following monomer pairs: styrene-acrylonitrile (AN), styrene-methyl methacrylate (MMA), styrene-2-methyl-5-vinylpyridine (MVP) and styrene- acrylic acid (AA) onto polyethylene film was studied at room temperature in the range of dose rates 8.10 -2-6.10 3 Gy/s. The grafted copolymer compositions were determined and copolymerization reactivity ratios were calculated. At high dose rates the contribution of the ionic mechanism is proved by the change of the copolymer compositions obtained at essential different dose rates and by different influence of the donor and acceptor solvents on this process. It is established that transition from radical mechanism to ionic one begins in the interval of dose rates 10 2-10 3 Gy/s for styrene-AN, styrene-MMA, styrene-MVP systems but occurs in the interval of dose rates 10 3-6.10 3 Gy/s for styrene-AA system. The formation of the grafted polymer compositions, obtained at high dose rates, must be described by the kinetics which takes into account the presence of ionic process.

Kabanov, V. Ya.; Aliev, R. E.

145

Importance of grafting in the emulsion polymerization of MMA using PVA as a protective colloid. Effect of initiators  

Microsoft Academic Search

To clarify the initial stage of particle formation in the emulsion polymerization of methyl methacrylate (MMA) using poly(vinyl alcohol) (PVA) as a protective colloid, a model experiment with a low concentration of MMA (1 ml\\/100 ml H2O) was carried out in the presence of various initiators, ammonium persulfate (APS), 2,2?-azobis(2-amidinopropane)dihydrochloride (V-50) and 2,2?-azobis (isobutyronitrile) (AIBN). In the experiments using a

Takuji Okaya; Atsushi Suzuki; Kenji Kikuchi

1999-01-01

146

Study of mass loss of spacecraft polymeric thermal control coatings under electron and proton radiations  

NASA Astrophysics Data System (ADS)

Polymeric composites have a number of properties that give a possibility to apply them as spacecraft external coatings. In space environment, however, such materials become one of the main sources of volatile products that form the outer spacecraft atmosphere and are able to con-dense on contamination-sensitive surfaces of onboard equipment. Thermal control coatings oc-cupy a considerable part of a satellite surface and are mostly subjected to ionizing radiations ac-companying by outgassing. The main stages of the process are the following: formation of vola-tile radiolysis products, diffusion of the products to free material surface, and desorption. Radia-tion-induced destruction and outgassing of material increase its permeability and accelerate mi-gration processes in it. Experimental data of effect of radiation on mass loss of polymeric composites used as thermal control coatings was analyzed and interpreted in the work. As a particular case, it was shown that mass loss of a polymeric composite irradiated by protons is greater than by electrons if energies and flux densities of the particles are the same. It can be explained that volatile products, in the first case, generate within a thin near-surface layer of material which permeability increases together with the absorbed dose, and quickly escape in vacuum. In the second case, a bulk of volatile products emerges far enough from the free surface of material which permeability increases slower as compared with proton radiation. Therefore, migration time of volatile products to the free surface grows and quantity of chemical reactions which they are involved in increases. To analyze and interpret experimental data, a mathematical model describing mass loss of polymeric composites subject to its growth of permeability under radiation is proposed. Based upon analysis of experiments and numerical simulation results, thresholds of fluen-cies and flux densities of electron and proton were determined. Exceeding these levels resulted in reducing thermal-induced mass loss of irradiated samples in comparison with the source mate-rial. These thresholds depend on energy and type of radiation.

Khasanshin, Rashid; Novikov, Lev; Galygin, Alexander

147

Grafting of poly(ethylene- block-ethylene oxide) onto a vapor grown carbon fiber surface by ?-ray radiation grafting  

Microsoft Academic Search

To modify the surface of vapor grown carbon fiber (VGCF), poly(ethylene-block-ethylene oxide) (PE-b-PEO, Mn=1400, PEO content=50wt%) was successfully grafted onto the surface by using ?-ray irradiation of the PE-b-PEO-adsorbed VGCF in solvent-free system. It is found that the percentage of polymer grafting reached 15.0% when the PE-b-PEO-adsorbed VGCF was irradiated by ?-ray over 40kGy dose at 110 °C, but at

Jinhua Chen; Gang Wei; Yasunari Maekawa; Masaru Yoshida; Norio Tsubokawa

2003-01-01

148

Ionic polymer-metal composite actuators obtained from radiation-grafted cation- and anion-exchange membranes.  

PubMed

Two series of ionic polymer-metal composites (IPMCs), one cationic and one anionic, are designed and prepared from radiation-grafted ion-exchange membranes. Through examination of the properties of the membranes synthesized from the two grafting monomers and the two base polymers, acrylic acid-grafted poly(vinylidene fluoride-co-hexafluoropropylene) and quarternized 4-vinylpyridine-grafted poly(ethylene-co-tetrafluoroethylene) with the appropriate amount of ionic groups are employed for the fabrication of cation and anion IPMCs, respectively. The bending displacement of the cation IPMC is comparable to Nafion-based IPMC under direct- and alternating-current voltage, but back-relaxation is not observed. The actuation performance of the anion IPMC is highly improved over those reported earlier in the literature for the other anion IPMCs. PMID:25420910

Park, Jong Hyuk; Han, Man Jae; Song, Dae Seock; Jho, Jae Young

2014-12-24

149

Uranium sorption by Pseudomonas biomass immobilized in radiation polymerized polyacrylamide bio-beads.  

PubMed

A Pseudomonas strain identified as a potent biosorbent of uranium (U) and thorium was immobilized in radiation-induced polyacrylamide matrix for its application in radionuclide containing wastewater treatment. The immobilized biomass exhibited a high U sorption of 202 mg g(-1) dry wt. with its optimum at pH 5.0. A good fit of experimental data to the Freundlich model suggested multilayered uranium binding with an affinity distribution among biomass metal binding sites. Scanning electron microscopy revealed a highly porous nature of the radiation-polymerized beads with bacterial cells mostly entrapped on pore walls. Energy dispersive X-ray analysis (EDXA) coupled with SEM ascertained the accumulation of uranium by the immobilized biomass without any physical damage to the cells. A significant (90%) part of biosorbed uranium was recovered using sodium bicarbonate with the immobilized biomass maintaining their U resorption capacity for multiple sorption-desorption cycles. Uranium loading and elution behavior of immobilized biomass evaluated within a continuous up-flow packed bed columnar reactor showed its effectiveness in removing uranium from low concentration (50 mg U L(-1)) followed by its recovery resulting in a 4-5-fold waste volume reduction. The data suggested the suitability of radiation polymerization in obtaining bacterial beads for metal removal and also the potential of Pseudomonas biomass in treatment of radionuclide containing waste streams. PMID:16484078

D'Souza, S F; Sar, Pinaki; Kazy, Sufia K; Kubal, B S

2006-01-01

150

Immobilization of yeast cells on hydrogel carriers obtained by radiation-induced polymerization  

NASA Astrophysics Data System (ADS)

Polymer hydrogels were obtained by radiation-induced copolymerization at -78°C of aqueous solutions of acrylic and methacrylic esters. The matrices were characterized by equilibrium water content measurements, by optical microscopy observations and by scanning electron microscopy analysis. Yeast cells were immobilized on these hydrogels and the ethanol productivity by batch fermentation was determined. Matrix hydrophilicity and porosity were found to deeply influence the adhesion of yeast cells and, hence, the ethanol productivity. The latter as well as other physico-chemical properties were also affected by the presence of a crosslinking agent added in small amounts to the polymerizing mixture.

Xin, Lu Zhao; Carenza, Mario; Kaetsu, Isao; Kumakura, Minoru; Yoshida, Masaru; Fujimura, Takashi

151

Detecting cells on the surface of a silver electrode quartz crystal microbalance using plasma treatment and graft polymerization.  

PubMed

This paper utilizes a silver electrode quartz crystal microbalance (QCM) mass sensor to detect the physiology of cells. This study also investigates the plasma surface modification of silver electrode QCMs through deposition of hexamethyldisilazane (HMDSZ) films as a protection film. To improve the cell growth, this paper also performs post-treatments by surface-grafting acrylic acid (AAc), acrylamide (AAm), and oxygen plasma treatment onto the QCM electrodes. Experimental results indicate that plasma deposition is a useful technique to protect the surface of silver electrodes. This technique extends the unpeeling time of silver electrodes from 1 to 7 days. The hydrophilic silver electrode QCM surface modified by AAm exhibited a better storage time effect than other post-treatments. PMID:19545984

Chou, Hung-Che; Yan, Tsong-Rong; Chen, Ko-Shao

2009-10-15

152

Synthesis of poly(N-isopropylacrylamide) hydrogels by radiation polymerization and cross-linking  

SciTech Connect

Poly(N-isopropylacrylamide) [poly(NIPAAm)] shows a typical thermal reversibility of phase transition in aqueous solutions. That is, it precipitates from solution above a critical temperature called the lower critical solution temperature (LCST) and dissolves below this temperature. When it is cross-linked, the obtained hydrogel collapses above LCST, while it swells and expands below LCST. This hydrogel has received much attention recently and has been used as a model system to demonstrate the validity of theories describing the coil-globule transition, swelling of networks, and folding and unfolding of biopolymers. It has also been proposed for various applications ranging from controlled drug delivery to solute separation. Poly(NIPAAm) hydrogel is usually synthesized at room temperature from an aqueous solution of the monomer by using a redox initiator composed of ammonium persulfate and N,N,N{prime},N{prime}-tetramethylethylenediamine in the presence of N,N{prime}-methylenebisacrylamide as a cross-linker. Since the LCST of poly(NIPAAm) is around 32 C, the polymerization at room temperature proceeds in a homogeneous solution. Recently, poly(NIPAAm) hydrogels were synthesized by starting the polymerization below the LCST and then elevating the temperature above it, by which method macroporous gels with fast temperature response were obtained. The idea is to apply a radiation--induced polymerization method for the synthesis of poly(NIPAAm) hydrogels. This method offers unique advantages for synthesis: it is a simple and additive-free process at all temperatures, and the degree of cross-linking can be easily controlled by irradiation conditions. Therefore, radiation methods are especially attractive for the synthesis of hydrogels with potential biomedical application where the residual chemical initiators may contaminate the product. It is possible to combine into one step the synthesis and sterilization of the product, and it is economically competitive.

Nagaoka, Noriyasu; Kubota, Hitoshi; Katakai, Ryoichi [Gunma Univ. (Japan). Dept. of Chemistry; Safranj, Agneza; Yoshida, Masaru; Omichi, Hideki [Japan Atomic Energy Research Inst., Gunma (Japan). Dept. of Material Development

1993-12-20

153

Hemocompatibility improvement of poly(ethylene terephthalate) via self-polymerization of dopamine and covalent graft of zwitterions.  

PubMed

Poly (ethylene terephthalate) (PET) has been widely adopted as a scaffold biomaterial, but further hemocompatibility improvement is still needed for wide biomedical applications. Inspired by the composition of adhesive proteins in mussels, we propose to use self-polymerized dopamine to form a surface-adherent polydopamine layer onto PET sheet, followed by Michael addition with N,N-dimethylethylenediamine (DMDA) to build tertiary amine, and final zwitterions(sulfobetaine and carboxybetaine) construction through ring-opening reaction. Physicochemical properties of substrates were demonstrated by water contact angle measurement, attenuated total reflection Fourier transform infrared spectroscopy (ATR-FTIR) and X-ray photoelectron spectroscopy (XPS). The hemocompatibility was evaluated by platelet adhesion, hemolytic, and protein adsorption. The results showed that the zwitterions immobilized PET endowed with improved resistance to nonspecific protein adsorption and platelet adhesion as well as nonhemolytic. The zwitterions with desirable hemocompatibility can be readily tailored to catheter for various biomedical applications. PMID:24433885

Cai, Xianmei; Yuan, Jiang; Chen, Shuangchun; Li, Pengfei; Li, Li; Shen, Jian

2014-03-01

154

Poly(glycidyl methacrylate) grafted CdSe quantum dots by surface-initiated atom transfer radical polymerization: Novel synthesis, characterization, properties, and cytotoxicity studies  

NASA Astrophysics Data System (ADS)

A novel approach for the synthesis of poly(glycidyl methacrylate) grafted CdSe quantum dot (QDs) (PGMA-g-CdSe) was developed. The PGMA-g-CdSe nanohybrids were synthesized by the surface-initiated atom transfer radical polymerization of glycidyl methacrylate from the surface of the strategic initiator, CdSe-BrIB QDs prepared by the interaction of 2-bromoisobutyryl bromide (BrIB) and CdSe-OH QDs. The structure, morphology, and optical property of the PGMA-g-CdSe nanohybrids were analyzed by FT-IR, XPS, TGA, XRD, TEM, and PL. The as-synthesized PGMA-g-CdSe nanohybrids having multi-epoxide groups were employed for the direct coupling of biotin via ring-opening reaction of the epoxide groups to afford the Biotin-f-PGMA-g-CdSe nanobioconjugate. The covalent immobilization of biotin onto PGMA-g-CdSe was confirmed by FT-IR, XPS, and EDX. Biocompatibility and imaging properties of the Biotin-f-PGMA-g-CdSe were investigated by MTT bioassay and PL analysis, respectively. The cell viability study suggested that the biocompatibility was significantly enhanced by the functionalization of CdSe QDs by biotin and PGMA.

Bach, Long Giang; Islam, Md. Rafiqul; Lee, Doh Chang; Lim, Kwon Taek

2013-10-01

155

Preparation of surface-imprinted polymer grafted with water-compatible external layer via RAFT precipitation polymerization for highly selective and sensitive electrochemical determination of brucine.  

PubMed

A novel brucine imprinted polymer was prepared on multi-walled carbon nanotubes by reversible addition-fragmentation chain transfer (RAFT) precipitation polymerization. The polymer was further grafted with hydrophilic poly(glycerol monomethacrylate) brushes to improve its water-compatibility. The obtained molecularly imprinted material showed enhanced accessibility to brucine and improved selective recognition property in water medium. When the material was supported on an ionic liquid functionalized graphene coated glassy carbon electrode for the electrochemical determination of brucine, the resulting electrochemical sensor presented good analytical performance. Under the optimized conditions, the peak current was linear to brucine concentration in the ranges of 0.006-0.6 ?M and 0.6-5.0 ?M with sensitivities of 15.3 ?A/?Mmm(2) and 5.4 ?A/?M mm(2), respectively; the detection limit was 2 nM (S/N=3). The sensor was successfully applied to the determination of brucine in practical samples and the recovery for the standards added was 94-104%. PMID:24769450

Zhao, Lijuan; Zhao, Faqiong; Zeng, Baizhao

2014-10-15

156

The effect of megavoltage radiation on polymeric materials to be used in biomedical devices.  

PubMed

For a number of biomedical applications, including the development of phantoms for quality control of radiotherapy treatments and dose determination, it is important to study the radiation response of the used materials, in order to distinguish the relevant dose distribution modifications from the artifacts caused by the phantom material when subjected to high dose irradiation. Beside the radiation response, those materials should have certain physical and chemical properties in order to be able to be used for the purposes described above, i.e., mechanical hardness and inelasticity, chemically stability and nonreactive, among others. In this work, a wide range of polymeric materials were irradiated under megavoltage radiation using a radiotherapy linear accelerator. The irradiated materials were imaged using transmission X-ray tomography to determine if some radiation induced electronic density change could result in altered Hounsfield units. Furthermore, Raman Spectroscopy and X-ray Diffraction (XRD) techniques were used before and after irradiation in order to study any structural modification induced by the radiation. In addition, a special phantom simulating a breast treatment with two tangential beams has been fabricated and tested. PMID:22962822

Neto, V F; Lencart, J; Dias, A G; Santos, J A M; Ramos, A; Relvas, C

2012-08-01

157

Gold-loaded polymeric micelles for computed tomography-guided radiation therapy treatment and radiosensitization.  

PubMed

Gold nanoparticles (AuNPs) have generated interest as both imaging and therapeutic agents. AuNPs are attractive for imaging applications since they are nontoxic and provide nearly three times greater X-ray attenuation per unit weight than iodine. As therapeutic agents, AuNPs can sensitize tumor cells to ionizing radiation. To create a nanoplatform that could simultaneously exhibit long circulation times, achieve appreciable tumor accumulation, generate computed tomography (CT) image contrast, and serve as a radiosensitizer, gold-loaded polymeric micelles (GPMs) were prepared. Specifically, 1.9 nm AuNPs were encapsulated within the hydrophobic core of micelles formed with the amphiphilic diblock copolymer poly(ethylene glycol)-b-poly(?-capralactone). GPMs were produced with low polydispersity and mean hydrodynamic diameters ranging from 25 to 150 nm. Following intravenous injection, GPMs provided blood pool contrast for up to 24 h and improved the delineation of tumor margins via CT. Thus, GPM-enhanced CT imaging was used to guide radiation therapy delivered via a small animal radiation research platform. In combination with the radiosensitizing capabilities of gold, tumor-bearing mice exhibited a 1.7-fold improvement in the median survival time, compared with mice receiving radiation alone. It is envisioned that translation of these capabilities to human cancer patients could guide and enhance the efficacy of radiation therapy. PMID:24377302

Al Zaki, Ajlan; Joh, Daniel; Cheng, Zhiliang; De Barros, André Luís Branco; Kao, Gary; Dorsey, Jay; Tsourkas, Andrew

2014-01-28

158

Radiation-induced graft copolymerization of poly(ethylene glycol) monomethacrylate onto deoxycholate-chitosan nanoparticles as a drug carrier  

NASA Astrophysics Data System (ADS)

Poly(ethylene glycol) monomethacrylate-grafted-deoxycholate chitosan nanoparticles (PEGMA-g-DCCSNPs) were successfully prepared by radiation-induced graft copolymerization. The hydrophilic poly(ethylene glycol) monomethacrylate was grafted onto deoxycholate-chitosan in an aqueous system. The radiation-absorbed dose is an important parameter on degree of grafting, shell thickness and particle size of PEGMA-g-DCCSNPs. Owing to their amphiphilic architecture, PEGMA-g-DCCSNPs self-assembled into spherical core-shell nanoparticles in aqueous media. The particle size of PEGMA-g-DCCSNPs measured by TEM varied in the range of 70-130 nm depending on the degree of grafting as well as the irradiation dose. Berberine (BBR) as a model drug was encapsulated into the PEGMA-g-DCCSNPs. Drug release study revealed that the BBR drug was slowly released from PEGMA-g-DCCSNPs at a mostly constant rate of 10-20% in PBS buffer (pH 7.4) at 37 °C over a period of 23 days.

Pasanphan, Wanvimol; Rattanawongwiboon, Thitirat; Rimdusit, Pakjira; Piroonpan, Thananchai

2014-01-01

159

Preparation of thermosensitive membranes by radiation grafting of acrylic acid/ N-isopropyl acrylamide binary mixture on PET fabric  

NASA Astrophysics Data System (ADS)

Thermosensitive membranes were prepared by radiation-induced graft copolymerization of monomers on PET fabrics. A binary mixture of N-isopropyl acrylamide (NIPAAm) and acrylic acid (AA) was grafted on polyester fabric as a base material to introduce thermosensitive poly( N-isopropyl acrylamide) pendant chains having LCST slightly higher than 37 °C in the membrane. The influence of ferrous sulfate, radiation dose and monomer composition on the degree of grafting was studied. The structure of the grafted fabric was characterized by thermogravimetric analysis, differential scanning calorimetry and scanning electron microscopy. The thermosensitive nature of the fabric was monitored by swelling at different temperatures. The graft copolymerization of AA with NIPAAm enhanced the LCST of the resultant membrane to ˜37 °C. The moisture vapor transmission rate (MVTR) and air permeability of the fabric decreased slightly, may be due to the slight blocking of the fabric pores. The immobilization of tetracycline hydrochloride as the model drug and its release characteristics at different temperatures were monitored.

Gupta, Bhuvanesh; Mishra, Swaiti; Saxena, Shalini

2008-05-01

160

Physicochemical aspects of the drugs radiation sterilization in commercial packing (applied scientific problems of radiation pharmaceutical chemistry)  

Microsoft Academic Search

The results of studies on the simultaneous radiosterilization of direct and bifurcational trachea prostheses made of silicon-organic rubber of soft elastic consistency, with polyethylenterephthalate and polyamid cuffs, and radiation chemical grafting of polymeric layer and linking with functional groups of the graft sulfanilamide and antibiotics layer are discussed. Radiopharmaceuticals are also described.

Safarov

1993-01-01

161

Study of radiation-grafted FEP-G-polystyrene membranes as polymer electrolytes in fuel cells  

Microsoft Academic Search

Proton exchange membranes for fuel cell applications were synthesized by pre-irradiation grafting of styrene\\/divinylbenzene mixtures into poly(fluoroethylene-co-hexafluoropropylene) films and subsequent sulfonation. Grafting of pre-existing films overcomes the problem of shaping the grafted polymer into thin membranes and makes this process a potentially cheap and easy technique for the preparation of solid polymer electrolytes.The grafted membranes were characterized by measuring their

Felix N. Büchi; Bhuvanesh Gupta; Otto Haas; Günther G. Scherer

1995-01-01

162

Radiation-induced grafting of multi-walled carbon nanotubes in glycidyl methacrylate maleic acid binary aqueous solution  

NASA Astrophysics Data System (ADS)

With the aim to improve the compatibility between multi-walled carbon nanotubes (MWCNTs) and nylon-6, purified MWCNTs ( p-MWCNTs) were grafted successfully with glycidyl methacrylate-maleic acid in aqueous solution using a single-step radiation method. The chemical structure and morphology of grafted p-MWCNTs ( g-MWCNTs) was investigated by micro-FTIR, Raman spectroscopy and transmission electron microscopy. The prepared nylon-6/ g-MWCNTs composite has higher mechanical strength and heat distortion temperature due to improved dispersion and compatibility than those of nylon-6/ p-MWCNTs.

Yu, Haibo; Mo, Xinyue; Peng, Jing; Zhai, Maolin; Li, Jiuqiang; Wei, Genshuan; Zhang, Xiaohong; Qiao, Jinliang

2008-05-01

163

Molecularly imprinted polymer membranes for substance-selective solid-phase extraction from water by surface photo-grafting polymerization.  

PubMed

Hydrophilized polyvinylidene fluoride microfiltration membranes were surface-modified in the presence of a template (terbumeton) in methanol with a graft copolymer of a functional monomer (2-acrylamido-2-methyl-1-propane sulfonic acid, AMPS, methacrylic acid, MAA, or acrylic acid, AA) and a cross-linker (N,N'-methylene-bis-acrylamide) using UV irradiation and benzophenone as photoinitiator. As result, membranes covered with a thin layer of imprinted polymer selective to terbumeton were obtained. Blank membranes were prepared with the same monomer composition, but in the absence of the template. The membranes' capacity to adsorb terbumetone from aqueous solution was evaluated yielding information regarding the effect of polymer synthesis (type and concentration of functional monomer, concentration of cross-linker) on the resulting membranes' recognition properties. UV spectroscopic studies of the interactions with terbumetone revealed that AMPS forms a stronger complex than MAA and AA. In agreement with that finding, imprinting with AMPS gave higher affinities than with MAA and AA. The terbumeton-imprinted membranes showed significantly higher sorption capability to this herbicide than to similar compounds (atrazine, desmetryn, metribuzine). With the novel surface modification technology, the low non-specific binding properties of the hydrophilized microfiltration membrane could successfully be combined with the receptor properties of molecular imprints, yielding substance-specific molecularly imprinted polymer composite membranes. The high affinity of these synthetic affinity membranes to triazine herbicides together with their straightforward and inexpensive preparation provides a good basis for the development of applications of imprinted polymers in separation processes such as solid-phase extraction. PMID:11217051

Sergeyev, T A; Matuschewski, H; Piletsky, S A; Bendig, J; Schedler, U; Ulbricht, M

2001-01-12

164

Electrospun regenerated cellulose nanofibrous membranes surface-grafted with polymer chains/brushes via the atom transfer radical polymerization method for catalase immobilization.  

PubMed

In this study, an electrospun regenerated cellulose (RC) nanofibrous membrane with fiber diameters of ?200-400 nm was prepared first; subsequently, 2-hydroxyethyl methacrylate (HEMA), 2-dimethylaminoethyl methacrylate (DMAEMA), and acrylic acid (AA) were selected as the monomers for surface grafting of polymer chains/brushes via the atom transfer radical polymerization (ATRP) method. Thereafter, four nanofibrous membranes (i.e., RC, RC-poly(HEMA), RC-poly(DMAEMA), and RC-poly(AA)) were explored as innovative supports for immobilization of an enzyme of bovine liver catalase (CAT). The amount/capacity, activity, stability, and reusability of immobilized catalase were evaluated, and the kinetic parameters (Vmax and Km) for immobilized and free catalase were determined. The results indicated that the respective amounts/capacities of immobilized catalase on RC-poly(HEMA) and RC-poly(DMAEMA) nanofibrous membranes reached 78 ą 3.5 and 67 ą 2.7 mg g(-1), which were considerably higher than the previously reported values. Meanwhile, compared to that of free CAT (i.e., 18 days), the half-life periods of RC-CAT, RC-poly(HEMA)-CAT, RC-poly(DMAEMA)-CAT, and RC-poly(AA)-CAT were 49, 58, 56, and 60 days, respectively, indicating that the storage stability of immobilized catalase was also significantly improved. Furthermore, the immobilized catalase exhibited substantially higher resistance to temperature variation (tested from 5 to 70 °C) and lower degree of sensitivity to pH value (tested from 4.0 and 10.0) than the free catalase. In particular, according to the kinetic parameters of Vmax and Km, the nanofibrous membranes of RC-poly(HEMA) (i.e., 5102 ?mol mg(-1) min(-1) and 44.89 mM) and RC-poly(DMAEMA) (i.e., 4651 ?mol mg(-1) min(-1) and 46.98 mM) had the most satisfactory biocompatibility with immobilized catalase. It was therefore concluded that the electrospun RC nanofibrous membranes surface-grafted with 3-dimensional nanolayers of polymer chains/brushes would be suitable/ideal as efficient supports for high-density and reusable enzyme immobilization. PMID:25396286

Feng, Quan; Hou, Dayin; Zhao, Yong; Xu, Tao; Menkhaus, Todd J; Fong, Hao

2014-12-10

165

Effects of solvents on the radiation grafting reaction of vinyl compounds on poly (3-hydroxybutyrate)  

NASA Astrophysics Data System (ADS)

Vinyl Acetate was grafted onto poly (3-hydroxybutyrate) by the simultaneous gamma irradiation method using different types of solvents and in bulk (solvent free), at 10 kGy and 1.62 kGy/h dose and dose rate respectively. Subsequent complete hydrolysis allowed the conversion of grafted chains from poly (vinyl acetate) to poly (vinyl alcohol). The aim of this study is to determine the effect of solvent through the estimation of the dependence of the degree of grafting with the choice of solvent, the calculation of the degree of crystallinity, and to study the biodegradation of the products. The results showed a greater degree of grafting in bulk, while the more suitable solvent was hexane. Characterization of the grafted copolymer indicated that crystallinity percentage decreased by an increase in grafting, while the biodegradability was promoted by the increment in poly (vinyl alcohol) grafted.

Torres, Maykel González; Talavera, José Rogelio Rodríguez; Muńoz, Susana Vargas; Pérez, Manuel González; Castro, Ma. Pilar. Carreón.; Cortes, Jorge Cerna; Muńoz, Rodrigo Alonso Esparza

2015-03-01

166

Immobilization of antibodies and enzyme-labeled antibodies by radiation polymerization  

SciTech Connect

Immobilization of antibodies and enzyme-labeled antibodies by radiation polymerization at low temperatures was studied. The antibody activity of antibody was not affected by irradiation at an irradiation dose of below 8 MR and low temperatures. Immobilization of peroxidase-labeled anti-rabbit IgG goat IgG, anti-peroxidase, peroxidase, and anti-alpha-fetoprotein was carried out with hydrophilic and hydrophobic monomers. The activity of the immobilized enzyme-labeled antibody membranes varied with the thickness of the membranes and increased with decreasing membrane thickness. The activity of the immobilized antibody particles was varied by particle size. Immobilized anti-alpha-fetoprotein particles and membranes can be used for the assay of alpha-fetoprotein by the antigen-antibody reaction, such as a solid-phase sandwich method with high sensitivity.

Kumakura, M.; Kaetsu, I.; Suzuki, M.; Adachi, S.

1983-04-01

167

Effects of ?-ray radiation grafting on aramid fibers and its composites  

NASA Astrophysics Data System (ADS)

Armos fiber was modified by Co 60 ?-ray radiation in the different concentrations' mixtures of phenol-formaldehyde and ethanol. Interlaminar shear strength (ILSS) was examined to characterize the effects of the treatment upon the interfacial bonding properties of Armos fibers/epoxy resin composites. The results showed that the ILSS of the composite, whose fibers were treated by 500 kGy radiation in 1.5 wt% PF, was improved by 25.4%. Nanoindentation technique analysis showed that the nanohardnesses of the various phases (the fiber, the interface and the matrix) in the composite, whose fibers were treated, were correspondingly higher than those in the composite, whose fibers were untreated. X-ray photoelectron spectroscopy (XPS) and Fourier transform infrared (FT-IR) spectrum confirmed the increase in the polar groups at the fibers' surface. Atomic force microscopy (AFM) results revealed that the surface of the fibers treated was rougher than that of the fibers untreated. The wettability of the fibers' surface was also enhanced by the treatment. The conclusion that ?-ray irradiation grafting significantly improved the surface properties of Armos fibers could be drawn.

Zhang, Y. H.; Huang, Y. D.; Liu, L.; Cai, K. L.

2008-03-01

168

Measurements of the temperature dependence of radiation induced conductivity in polymeric dielectrics  

NASA Astrophysics Data System (ADS)

This study measures Radiation Induced Conductivity (RIC) in five insulating polymeric materials over temperatures ranging from ~110 K to ~350 K: polyimide (PI or Kapton HN(TM) and Kapton E(TM)), polytetraflouroethylene (PTFE or Teflon(TM)), ethylene-tetraflouroethylene (ETFE or Tefzel(TM)), and Low Density Polyethylene (LDPE). RIC occurs when incident ionizing radiation deposits energy and excites electrons into the conduction band of insulators. Conductivity was measured when a voltage was applied across vacuum-baked, thin film polymer samples in a parallel plate geometry. RIC was calculated as the difference in sample conductivity under no incident radiation and under an incident ~4 MeV electron beam at low incident dose rates of 0.01 rad/sec to 10 rad/sec. The steady-state RIC was found to agree well with the standard power law relation, sigmaRIC(D?) = kRIC(T) D?Delta(T) between conductivity, sigmaRIC and adsorbed dose rate, D?. Both the proportionality constant, kRIC, and the power, Delta, were found to be temperature-dependent above ~250 K, with behavior consistent with photoconductivity models developed for localized trap states in disordered semiconductors. Below ~250 K, kRIC and Delta exhibited little change in any of the materials.

Gillespie, Jodie

169

Polymerization as a limiting factor for light product yields in radiation cracking of heavy oil and bitumen  

NASA Astrophysics Data System (ADS)

The kinetic model of radiation-thermal and low-temperature radiation cracking is developed subject to the specificity of radiation-induced processes and the effect of structure in extremely heavy hydrocarbon feedstock. Theoretical calculations are compared with the available experimental data. The dependences of the cracking product yields on temperature, dose and dose rate of ionizing irradiation are analyzed on the base of the developed model subject to the structural state of the feedstock. Radiation-induced polymerization and chemical adsorption are considered as the important factors limiting heavy oil conversion.

Zaikin, Yuriy A.; Zaikina, Raissa F.

2013-03-01

170

Modification of polyethylene films by radiation grafting of glycidyl methacrylate and immobilization of ?-cyclodextrin  

NASA Astrophysics Data System (ADS)

Glycidyl methacrylate was grafted onto polyethylene films using a preirradiation method with ? rays. The effect of absorbed dose, monomer concentration, and reaction time on the degree of grafting was determined. The grafted samples were verified by FTIR-ATR spectroscopy. ?-Cyclodextrin was immobilized onto polypropylene modified with glycidyl methacrylate, and the ability of the cavities of ?-cyclodextrin to form inclusion complexes was demonstrated using the typically organic compound approach with m-toluic acid (3-MBA) as a probe.

Nava-Ortiz, C. A. B.; Burillo, G.; Bucio, E.; Alvarez-Lorenzo, C.

2009-01-01

171

Radiation grafting of acrylic and methacrylic acid to cellulose fibers to impart high water sorbency  

SciTech Connect

Acrylic and methacrylic acids have been directly grafted to rayon and cotton using the preirradiation technique with /sup 60/ Co gamma rays. The rate of grafting increased with increasing temperature and monomer concentration, as did the final degree of grafting. The amount and rate of grafting also increased with the total irradiation dose but tended to level off at higher doses, in agreement with the leveling off of the radical content reported previously. Methacrylic acid grafted more and faster than acrylic acid to both rayon and cotton. Methacrylic acid grafted more with rayon than cotton, but acrylic acid gave somewhat similar yields with both fibers. The water abosrbency of the grafted fibers depended strongly on their posttreatment. Decrystallizing with 70% zinc chloride or with hot sodium hydroxidy developed supersorbency. The two treatments in succession, respectively, gave the highest values. Metacrylic acid brought about less sorbency than the corrsponding acrylic acid grafts. Useful levels of grafting and supersorbency could be readily and practically achieved by the methods described.

Zahran, A.H.; Williams, J.L.; Stannett, V.T.

1980-04-01

172

Immobilization of yeast cells with polymeric carrier cross-linked using radiation technique.  

PubMed

Various compositions of 2-hydroxyethacrylate (HEA) and methoxy polyethylene glycol methacrylate (M23G) monomers were irradiated by gamma-rays at low temperature (-78 degrees C) to synthesize polymer carriers for effectively immobilizing yeast cells. The yeast cells were immobilized by cell adhesion onto/in these polymers. The ethanol productivity of immobilized yeast cells with the polymer carriers was higher than that of free cells, increasing by 1-3 times. However, the ethanol productivity of immobilized yeast with the polymer carrier resulting from 7%/7% (HEA/M23G) monomer was low, comparatively. The effect of adding cross-linking reagent (4G) to the low concentration of HEA/M23G monomers on the activity of yeast cells immobilized with the cross-linked carriers by radiation polymerization was investigated. The ethanol productivity of immobilized cells with the carriers, which were cross-linked by adding 3-6% 4G to the low concentration of HEA/M23G monomer, was increased by 20-30%, because the pore size, network structure, and mechanical strength of the polymer carriers was well adjusted and cell leakage from the polymer carriers decreased. The relationship between the ethanol productivity of immobilized yeast cells and the interior structure of polymer carriers is discussed and indicated that the interior structure of polymer carriers is crucial for effective immobilization of yeast cells. PMID:11982402

Zhaoxin, Lu; Fengxia, Lu; Bie Xiaomei, Bie; Fujimura, Takashi

2002-05-01

173

Fabrication and mechanical characterization of biodegradable and synthetic polymeric films: Effect of gamma radiation  

NASA Astrophysics Data System (ADS)

Chitosan (1 wt%, in 2% aqueous acetic acid solution) and starch (1 wt%, in deionised water) were dissolved and mixed in different proportions (20-80 wt% chitosan) then films were prepared by casting. Tensile strength and elongation at break of the 50% chitosan containing starch-based films were found to be 47 MPa and 16%, respectively. It was revealed that with the increase of chitosan in starch, the values of TS improved significantly. Monomer, 2-butane diol-diacrylate (BDDA) was added into the film forming solutions (50% starch-based), then casted films. The BDDA containing films were irradiated under gamma radiation (5-25 kGy) and it was found that strength of the films improved significantly. On the other hand, synthetic petroleum-based polymeric films (polycaprolactone, polyethylene and polypropylene) were prepared by compression moulding. Mechanical and barrier properties of the films were evaluated. The gamma irradiated (25 kGy) films showed higher strength and better barrier properties.

Akter, Nousin; Khan, Ruhul A.; Salmieri, Stephane; Sharmin, Nusrat; Dussault, Dominic; Lacroix, Monique

2012-08-01

174

Adsorption of Cr(VI) using cellulose microsphere-based adsorbent prepared by radiation-induced grafting  

NASA Astrophysics Data System (ADS)

Cellulose microsphere (CMS) adsorbent was prepared by radiation-induced grafting of dimethylaminoethyl methacrylate (DMAEMA) onto CMS followed by a protonation process. The FTIR spectra analysis proved that PDMAEMA was grafted successfully onto CMS. The adsorption of Cr(VI) onto the resulting adsorbent was very fast, the equilibrium adsorption could be achieved within 15 min. The adsorption capacity strongly depended on the pH of the solution, which was attributed to the change of both the existed forms of Cr(VI) and the tertiary-ammonium group of PDMAEMA grafted CMS with the pH. A maximum Cr(VI) uptake (ca. 78 mg g-1) was obtained as the pH was in the range of 3.0-6.0. However, even in strong acid media (pH 1.3), the adsorbents still showed a Cr(VI) uptake of 30 mg g-1. The adsorption behavior of the resultant absorbent could be described with the Langmuir mode. This adsorbent has potential application for removing heavy metal ion pollutants (e.g. Cr(VI)) from wastewater.

Li, Cancan; Zhang, Youwei; Peng, Jing; Wu, Hao; Li, Jiuqiang; Zhai, Maolin

2012-08-01

175

Polymeric Materials With Additives for Durability and Radiation Shielding in Space  

NASA Technical Reports Server (NTRS)

Polymeric materials are attractive for use in space structures because of their light weight and high strength In addition, polymers are made of elements with low atomic numbers (Z), primarily carbon (C), hydrogen (H), oxygen (0), and nitrogen (N) which provide the best shielding from galactic cosmic rays (GCR) (ref. 1). Galactic cosmic rays are composed primarily of nuclei (i.e., fully ionized atoms) plus a contribution of about 2% from electrons and positrons. There is a small but significant component of GCR particles with high charge (Z > 10) and high energy (E >100 GeV) (ref. 2). These so-called HZE particles comprise only 1 to 2% of the cosmic ray fluence but they interact with very high specific ionization and contribute 50% of the long- term dose to humans. The best shield for this radiation would be liquid hydrogen, which is not feasible. For this reason, hydrogen-containing polymers make the most effective practical shields. Moreover, neutrons are formed in the interactions of GCR particles with materials. Neutrons can only lose energy by collisions or reactions with a nucleus since they are uncharged. This is a process that is much less probable than the Coulombic interactions of charged particles. Thus, neutrons migrate far from the site of the reaction in which they were formed. This increases the probability of neutrons reaching humans or electronic equipment. Fast neutrons (> 1 MeV) can interact with silicon chips in electronic equipment resulting in the production of recoil ions which can cause single event upsets (SEU) in sensitive components (ref. 3). Neutrons lose energy most effectively by elastic collisions with light atoms, particularly hydrogen atoms. Therefore, hydrogen-containing polymers are not only effective in interacting with GCR particles; they are also effective in reducing the energy of the neutrons formed in the interactions.

Kiefer, Richard

2011-01-01

176

Skin graft  

MedlinePLUS

Skin transplant; Skin autografting; FTSG; STSG; Split thickness skin graft; Full thickness skin graft ... donor site. Most people who are having a skin graft have a split-thickness skin graft. This takes ...

177

Release characteristics of diclofenac sodium from poly(vinyl alcohol)\\/sodium alginate and poly(vinyl alcohol)-grafted-poly(acrylamide)\\/sodium alginate blend beads  

Microsoft Academic Search

In this study, acrylamide (AAm) was grafted onto poly(vinyl alcohol) (PVA) with UV radiation at ambient temperature. The graft copolymer (PVA-g-PAAm) was characterized by using Fourier transform infrared spectroscopy (FTIR), elemental analysis and differential scanning calorimetry (DSC). Polymeric blend beads of PVA-g-PAAm and PVA with sodium alginate (NaAlg) were prepared by cross-linking with glutaraldehyde (GA) and used to deliver a

Oya ?anl?; Nuran Ay; Nuran I??klan

2007-01-01

178

Free radical graft copolymerization of nanofibrillated cellulose with acrylic monomers  

Microsoft Academic Search

Nanofibrillated cellulose (NFC) was graft copolymerized in aqueous suspension by a redox-initiated free radical method. Cerium ammonium nitrate was used as initiator. Acrylic monomers used in the grafting were glycidyl methacrylate, ethyl acrylate, methyl methacrylate, butyl acrylate, and 2-hydroxyethyl methacrylate. Effects of monomer type and concentration, initiator concentration and polymerization time on grafting from NFC were studied. Grafting was verified

Kuisma Littunen; Ulla Hippi; Leena-Sisko Johansson; Monika Österberg; Tekla Tammelin; Janne Laine; Jukka Seppälä

2011-01-01

179

Fire proofing by radiation grafting (application on polyester and polypropylene). Scientific technical report  

Microsoft Academic Search

This report outlines efforts to try out a modern technique, radition grafting, rather than chemical and heat fixation, to make textiles more fire-proof by reducing as much as possible the deterioration in conventional properties, in particular softness and handle, to which the former give rise. The expected consequences are twofold: possession of a general method for fire-proofing textile materials which

B. J. Hill; U. Einsele; G. Di Modica; D. Wattiez

1980-01-01

180

A mild method of amine-type adsorbents syntheses with emulsion graft polymerization of glycidyl methacrylate on polyethylene non-woven fabric by pre-irradiation  

NASA Astrophysics Data System (ADS)

A mild pre-irradiation method was used to graft glycidyl methacrylate (GMA) onto polyethylene (PE) non-woven fabric (NF). The polymer was irradiated by electron beam in air atmosphere at room temperature. The degree of grafting (Dg) was determined as a function of reaction time, absorbed dose, monomer concentration and temperature. After 30 kGy irradiation, with 5% GMA, surfactant Tween 20 (Tw-20) of 0.5% at 55 °C for 15 min, the trunk polymer was made grafted with a Dg of 150%. Selected PE-g-PGMA of different Dg was modified with aminated compounds such as ethylenediamine (EDA), diethylenetriamine (DETA), triethylenetetramine (TETA) and tetraethylenepentamine (TEPA). The obtained amine-type adsorbents were prepared to remove copper and uranium ions from solution. It was shown that at least 90% of copper and 60% of uranium with the initial concentration from 3 to 1000 ppb can be removed from water.

Ma, Hongjuan; Yao, Side; Li, Jingye; Cao, Changqing; Wang, Min

2012-09-01

181

Gamma-ray co-irradiation induced graft polymerization of NVP and SSS onto polypropylene non-woven fabric and its blood compatibility  

NASA Astrophysics Data System (ADS)

Sodium styrenesulfonate was grafted onto PPNWF via ?-ray co-irradiation method with the existence of N-vinyl-2-pyrrolidone. The effect of absorbed dose, dose rate and concentration of binary monomer on the degree of grafting was investigated. The surface chemical change was characterized by attenuated total reflection Fourier transform infrared spectroscopy (ATR-FTIR) and X-ray photoelectron spectroscopy (XPS). The wettability was characterized through the measurement of adsorption percentage of water and phosphate buffer solution (PBS). The result demonstrated that the grafted poly(NVP-co-SSS) chains can improve the hydrophilicity of PPNWF. Furthermore, the modified PPNWF has good blood compatibility, such as low hemolysis rate, low platelet adhesion and effectively extending the blood coagulation times. Consequently, hydrophilicity and hemocompatibility of PPNWF were greatly enhanced by the immobilization of poly(NVP-co-SSS) chains.

Li, Rong; Wang, Hengdong; Wang, Wenfeng; Ye, Yin

2013-10-01

182

Radiation-grafting of 4-vinylpyridine and N-isopropylacrylamide onto polypropylene to give novel pH and thermo-sensitive films  

NASA Astrophysics Data System (ADS)

Here 4-vinylpyridine (4VP) was grafted onto polypropylene films (PP) by mutual irradiation method to give PP-g-4VP; N-isopropylacrylamide (NIPAAm) was then grafted onto the PP-g-4VP films to give (PP-g-4VP)-g-NIPAAm by pre-irradiation method, using a 60Co ?-source. The dependence of grafting percentage on radiation dose, temperature, reaction time, and monomer concentration was studied. (PP-g-4VP)-g-NIPAAm films were characterized by infrared spectroscopy (FTIR-ATR), differential scanning calorimetry (DSC), and thermogravimetric analysis (TGA). The critical pH point and lower critical solution temperature (LCST) were determined by swelling and water contact angle measurements. The LCST also was determined by DSC. The binary graft copolymer films are shown to be thermo-pH sensitive.

Meléndez-Ortiz, H. I.; Bucio, E.; Burillo, G.

2009-01-01

183

Surface modification of polyethylene by radiation-induced grafting for adhesive bonding. IV. Improvement in wet peel strength. [Gamma radiation  

Microsoft Academic Search

Adhesive joints of hydrolyzed methyl acrylate grafts, bonded with epoxy adhesives, yield extremely high peel strength (adherend failure) in dry conditions. However, when the joints are exposed to humid environments, the peel strength rapidly decreases with exposure time and then reaches a constant value (wet peel strength). Since the locus of failure changes from the adherend to the homopolymer layer

S. Yamakawa; F. Yamamoto

1980-01-01

184

Effect of carbon-black treatment by radiation emulsion polymerization on temperature dependence of resistivity of carbon-black-filled polymer blends  

NASA Astrophysics Data System (ADS)

High dispersibility and stability of carbon black particles in low-density-polyethylene (LDPE) matrix were obtained by radiation emulsion polymerization on carbon particles surface, and electrical resistivities of its simple were examined. First carbon particles treatment on radiation emulsion polymerization on surface were synthesized by the reaction with a polymer-emulsion systems containing reactive group in the molecular unit, carbon particles and emulsifier. Then, the carbon particles treatment on radiation emulsion polymerization on surface was dispersed into LDPE, and its composites were prepared for electrical measurements. The effect of radiation crosslinking of the composite on the Positive temperature coefficient (PTC) and negative temperature coefficient (NTC) phenomenon was investigated. The experimental results showed that PTC and NTC effects of the composites were obviously influenced by the irradiation dose. Various microstructure-exploring means were used to study the conductive composite, such as scanning electron microscopy (SEM), X-ray diffraction (XRD) and transmission electron microscopy (TEM).

Shaojin, Jia; Pingkai, Jiang; Zhicheng, Zhang; Zhongguang, Wang

2006-04-01

185

Evaluation of Thermal Control Coatings and Polymeric Materials Exposed to Ground Simulated Atomic Oxygen and Vacuum Ultraviolet Radiation  

NASA Technical Reports Server (NTRS)

Numerous thermal control and polymeric samples with potential International Space Station applications were evaluated for atomic oxygen and vacuum ultraviolet radiation effects in the Princeton Plasma Physics Laboratory 5 eV Neutral Atomic Oxygen Facility and in the MSFC Atomic Oxygen Drift Tube System. Included in this study were samples of various anodized aluminum samples, ceramic paints, polymeric materials, and beta cloth, a Teflon-impregnated fiberglass cloth. Aluminum anodizations tested were black duranodic, chromic acid anodize, and sulfuric acid anodize. Paint samples consisted of an inorganic glassy black paint and Z-93 white paint made with the original PS7 binder and the new K2130 binder. Polymeric samples evaluated included bulk Halar, bulk PEEK, and silverized FEP Teflon. Aluminized and nonaluminized Chemfab 250 beta cloth were also exposed. Samples were evaluated for changes in mass, thickness, solar absorptance, and infrared emittance. In addition to material effects, an investigation was made comparing diffuse reflectance/solar absorptance measurements made using a Beckman DK2 spectroreflectometer and like measurements made using an AZ Technology-developed laboratory portable spectroreflectometer.

Kamenetzky, R. R.; Vaughn, J. A.; Finckenor, M. M.; Linton, R. C.

1995-01-01

186

Poly (acryloyl- L-proline methyl ester) hydrogels obtained by radiation polymerization for the controlled release of drugs  

NASA Astrophysics Data System (ADS)

Thermosensitive hydrogels were obtained by radiation-induced polymerization of acryloyl- L-proline methyl ester in the presence of a crosslinking agent. The measurements of equilibrium water content in the temperature range between 0° and 60°C showed that the samples swelled at low temperatures while they shrank at high temperatures. These hydrogels were used as drug delivery systems for the controlled release of insulin. In vivo studies carried out on diabetic rats ascertained a significant reduction in the hyperglycemic level in the blood which continued for about 2 months.

Carenza, M.; Caliceti, P.; Veronese, F. M.; Martellini, F.; Higa, O. Z.; Yoshida, M.; Katakai, R.

2000-03-01

187

Adsorption of uranium ions by resins with amidoxime and amidoxime/carboxyl group prepared by radiation-induced polymerization  

NASA Astrophysics Data System (ADS)

In order to recover uranium ions from seawater, chelate-type resins with amidoxime and amidoxime/carboxylic acid groups were prepared by radiation-induced polymerization of acrylonitrile (AN) and AN/acrylic acid and by subsequent amidoximation of cyano group of poly(AN), respectively. The resins were characterized by FT-IR, FT-Raman, solid-state 13C-NMR, SEM, and elemental analysis, respectively. The adsorption rate of uranium ion by resins with the amidoxime/carboxylic acid group were higher than that of resins with the amidoxime group. The adsorption of uranium ions in artificial seawater to chelate-type resins was also examined.

Choi, Seong-Ho; Choi, Min-Seok; Park, Yong-Tae; Lee, Kwang-Pill; Kang, Hee-Dong

2003-06-01

188

In-situ polymerization of vinyl pyrrolidinone on nylon 66 by gamma radiation  

SciTech Connect

The polymerization of vinyl pyrrolidinone on nylon 66, with the assistance of aqueous phenol and formic acid, was investigated by mutual and post irradiation procedures. Both solvents were found to greatly facilitate the polymerization with the post irradiation procedure, whereas neither presented any advantage with the mutual irradiation procedure. Tensile properties of the modified fibers were affected in similar ways by both the irradiation procedures and solvents in that the only notable changes were the somewhat higher extensions at yield and at break. The moisture regain values of the treated yarns and fabrics were increased up to three-fold. Surface morphology of the modified fibers was revealed by SEM.

Hsieh, Y.L.; Potter, D.; Ellison, M.S.

1984-10-01

189

Mechanical properties of tough hydrogels synthesized with a facile simultaneous radiation polymerization and cross-linking method  

NASA Astrophysics Data System (ADS)

Radiation-induced polymerization and cross-linking method has been applied to hydrogel preparations for decades, but less attention has been paid to the mechanical properties of the hydrogels. In this work, we provide a systematic study on the mechanical properties of hydrogels synthesized with the simultaneous radiation polymerization and cross-linking method. The prepared polyacrylamide (PAAm) had very good mechanical properties, namely high compressive strengths (several to more than 10 MPa), high tensile strengths (up to 260 kPa), high fracture strains (up to 12) and high fracture energies (10-160 J/m2). Absorbed dose and monomer concentration were the two important factors affecting the mechanical properties of the gels. The compressive strength and elastic modulus of the gels increased with increasing absorbed dose and monomer concentration, while the tensile strength, fracture strain and fracture energy of the gels decreased with increasing absorbed dose. The gels also showed excellent elastic recovery property, as indicated by the low stress-strain hysteresis ratios in cyclic tensile tests as well as the small loss factors measured with dynamic mechanical analysis (DMA).

Jiang, Fangzhi; Wang, Xuezhen; He, Changcheng; Saricilar, Sureyya; Wang, Huiliang

2015-01-01

190

Development of novel hydrogels by modification of sterculia gum through radiation cross-linking polymerization for use in drug delivery  

NASA Astrophysics Data System (ADS)

In order to modify the sterculia gum polysaccharide, to develop the hydrogels meant for the drug delivery, we have prepared sterculia gum, 2-hydroxyethylmethacrylate (HEMA) and acrylic acid (AAc) based hydrogels by radiation-induced crosslinking polymerization. Polymeric networks (hydrogels) thus formed were characterized with SEMs, FTIR,TGA and swelling studies which were carried out as a function monomers concentration, radiation dose, amount of sterculia contents in the polymer matrix and nature of the swelling medium. This paper discusses the swelling kinetics of the hydrogels and release dynamics of anti-diarrhea model drug ornidazole from the hydrogels to evaluation of swelling and drug release mechanism. Diffusion exponent ' n' have 0.73, 0.56 and 0.61 values and gel characteristic constant ' k' have 1.28 × 10 -2, 2.95 × 10 -2 and 2.14 × 10 -2 values in distilled water, pH 2.2 buffer and pH 7.4 buffer. The release of drug from the polymer matrix occurred through non-Fickian diffusion mechanism. The values for the late time diffusion coefficients have been lower than the values of initial and average diffusion coefficients. It reflects that in the initial stages rate of release of drug from polymer matrix was higher as compared to the late stages, it means after certain time the drug release occurred in controlled manner.

Singh, Baljit; Vashishtha, Manu

2008-05-01

191

Graft polymerization of acrylic acid onto polyethylene film by preirradiation method. I. Effects of preirradiation dose, monomer concentration, reaction temperature, and film thickness. [Electron beams  

Microsoft Academic Search

Low- and high-density polyethylenes were irradiated by electron beams with dose of 2 to 50 Mrad and then immersed in aqueous solution of acrylic acid (monomer concentration from 30 to 100 wt %) for 10 min to 5h at a temperature of 25 to 40°C. The degree of grafting increases with time and levels off. High density polyethylene shows lower

I. Ishigaki; T. Sugo; K. Senoo; T. Okada; J. Okamoto; S. Machi

1982-01-01

192

Surface-initiated atom transfer radical polymerization of polyamine grafting from magnetic iron oxide submicroparticles for high adsorption capacity of cadmium in aqueous solution.  

PubMed

Chemical modification of magnetic submicroparticles (MSPs) with functional polymers using controlled/living radical polymerization method has recently gained a great deal of attentions because of the potential applications to water treatment. In this work, we demonstrated an efficient method for poly(glycidyl methacrylate) (pGMA) modification of MSPs, by surface-initiated atom transfer radical polymerization method, and then, the particles were actually modified by triethylenetetramine through epoxy groups of pGMA to form polyamine/MSPs. The material was characterized using infrared spectroscopy, thermo gravimetric analyzer, transmission electron microscopic, gel permeation chromatography, and vibrating sample magnetometer. Sorption of Cd(II) to polyamine/MSPs reached equilibrium in ~100 min and agreed well to the Freundlich isotherm equation with maximum adsorption capacity of 71.3 mg g(-1) for the 500 mg L(-1) Cd(II) aqueous solution at neutral pH. PMID:23273544

Liu, Qingyang; Ji, Zhongxing; Bei, Yiling

2013-03-15

193

Dosimetry for an Sr 90\\/Y 90 source train used for intravascular radiation of a hemodialysis graft  

Microsoft Academic Search

ObjectiveVascular access for hemodialysis is often achieved with an arterial–venous graft (AVG). Brachytherapy is being explored for prevention of stenosis within these grafts. The objective was to develop treatment planning (TP) capability for dialysis implants.

Peter Bloch; Raoul Bonan; Paul Wallner; John Lobdell

2003-01-01

194

Effect of ?-ray irradiation grafting on the carbon fibers and interfacial adhesion of epoxy composites  

Microsoft Academic Search

A special technique using ?-ray irradiation-induced graft-polymerization was applied to carbon fibers. Epoxy resin and chloroepoxy propane reacted with carbon fibers by a co-irradiation grafting method and acrylic acid was graft-polymerized onto the fiber surface via a pre-irradiation grafting method. The roughness, amount of containing-oxygen functional groups and surface energy were all found to increase significantly after irradiation grafting. Gamma-ray

Zhiwei Xu; Yudong Huang; Chunhua Zhang; Li Liu; Yanhua Zhang; Lei Wang

2007-01-01

195

Graft Copolymerization of Vinyl Monomers onto Cellulose and Cellulosic Materials  

Microsoft Academic Search

Graft copolymerization is a novel method which has wide application in synthesizing new forms of polymeric materials and also in modifying the properties of natural polymers [1,2]. Much research has been done on grafting polymeric molecules on to cellulose to produce materials of new properties intermediate between those of cellulose and those of synthetics. A variety of property changes can

Munmaya K. Mishra

1982-01-01

196

Radiation-induced graft copolymerization of methyl methacrylate on natural and modified wool. V. Crystalline and morphological structure. [. gamma. -rays  

SciTech Connect

X-ray diffraction patterns of the ..cap alpha..- and ..beta..-crystalline phases of natural, chemically modified, and MMA-grafted wool fibers were investigated. In the grafted fibers variation of the equatorial and meridional scattering intensity during the ..cap alpha..-..beta.. transformation was inhibited. This indicated that the grafting had stabilized the structure to the ..cap alpha..-..beta.. transformation. The average crystallite size was found to increase with the extent of grafting, and the degree of orientation appeared to decrease with percent graft-on. SEM studies revealed little damage to the surface topography of wool fibers after chemical treatments. Graft copolymerization with MMA made the fiber surface regular and smooth, mainly because of deposition of polymer in the escarpment, thus reducing the sharpness of the scaly structure. Scanning electron micrographs of the peeled-off surface and cross sections of the grafted fibers indicated that a significant amount of polymer was deposited in the medullae of the fibers.

Varma, D.S.; Sadhir, R.K.

1980-03-01

197

Chemically grafted polymeric filters for chemical sensors: Hyperbranched poly(acrylic acid) films incorporating {Beta}-cyclodextrin receptors and amine-functionalized filter layers  

SciTech Connect

The authors report a new molecular-filter approach for enhancing the selectivity of chemical sensors. Specifically, they describe electrochemical sensors prepared from Au electrodes coated with {beta}-cyclodextrin-functionalized, hyperbranched poly(acrylic acid)(PAA) films capped with a chemically grafted, ultrathin polyamine layer. The hyperbranched PAA film is a highly functionalized framework for covalently binding the {beta}-cyclodextrin molecular receptors. The thin, grafted polyamine overlayer acts as a pH-sensitive molecular filter that selectively passes suitably charged analytes. Poly(amidoamine) dendrimers or poly-D-lysine is used as 10--15-nm-thick filter layers. The results show that at low pH, when the polyamines are fully protonated, positively charged redox probe molecules, such as benzyl viologen (BV), do not permeate the filter layer. However, at high pH, when the filter layer is uncharged, BV penetrates the filter layer and is reduced at the electrode. The opposite pH dependence is observed for negatively charged redox molecules such as anthraquinone-2-sulfonate (AQS). Both BV and AQS specifically interact with the {beta}-cyclodextrin receptors underlying the polyamine filter layers.

Dermody, D.L.; Peez, R.F.; Bergbreiter, D.E.; Crooks, R.M. [Texas A and M Univ., College Station, TX (United States). Dept. of Chemistry] [Texas A and M Univ., College Station, TX (United States). Dept. of Chemistry

1999-02-02

198

Development of high-productivity, strong cation-exchange adsorbers for protein capture by graft polymerization from membranes with different pore sizes  

PubMed Central

This paper describes the surface modification of macroporous membranes using ATRP (atom transfer radical polymerization) to create cation-exchange adsorbers with high protein binding capacity at high product throughput. The work is motivated by the need for a more economical and rapid capture step in downstream processing of protein therapeutics. Membranes with three reported nominal pore sizes (0.2, 0.45, 1.0 ?m) were modified with poly(3-sulfopropyl methacrylate, potassium salt) tentacles, to create a high density of protein binding sites. A special formulation was used in which the monomer was protected by a crown ether to enable surface-initiated ATRP of this cationic polyelectrolyte. Success with modification was supported by chemical analysis using Fourier-transform infrared spectroscopy and indirectly by measurement of pure water flux as a function of polymerization time. Uniformity of modification within the membranes was visualized with confocal laser scanning microscopy. Static and dynamic binding capacities were measured using lysozyme protein to allow comparisons with reported performance data for commercial cation-exchange materials. Dynamic binding capacities were measured for flow rates ranging from 13 to 109 column volumes (CV)/min. Results show that this unique ATRP formulation can be used to fabricate cation-exchange membrane adsorbers with dynamic binding capacities as high as 70 mg/mL at a throughput of 100 CV/min and unprecedented productivity of 300 mg/mL/min. PMID:23175597

Chenette, Heather C.S.; Robinson, Julie R.; Hobley, Eboni; Husson, Scott M.

2012-01-01

199

Methods of fiber surface grafting for interphase design and tailored composite response  

NASA Astrophysics Data System (ADS)

The objective of this research was to develop methods of fiber surface grafting for interphase formation, and to experimentally evaluate and model these interphases in order to further elucidate their role in fiber-reinforced composites. Surface modification by sp{60}Co gamma irradiation was used initially to graft acrylic polymers on the surface of ultra-high modulus (UHMPE) fibers. This technique utilized low dose rates and low total doses, and achieved grafting with retention of the exceptional UHMPE properties. The surface properties of the fibers were evaluated using fourier transform infra-red spectroscopy (FTIR), electron spectroscopy for chemical analysis (ESCA), and mechanical tests and dynamic mechanical spectrometry (DMS) of discontinuous fiber composites. Depending on the glass transition temperature, Tg, and chemical structure of the graft, the fiber/matrix adhesion and the interfacial failure mechanism was tailored to provide either enhanced reinforcement or toughening. Using a three-phase block model, the DMS characteristics of the composites were modeled and the reinforcement efficiencies extrapolated as a function of surface treatment. The model successfully predicts the tan delta response of the composite and the appearance of additional loss dispersions associated with the interphase. However, the interactions between the high-energy gamma radiation and the fiber and grafts yield interphases that are difficult to characterize and control. The hydroperoxidation grafting method was subsequently developed, which permitted the grafting of tethered, linear chains by a free radical-type polymerization. Poly(styrene-stat-acrylonitrile) was grafted initially, in which the nitrogen in acrylonitrile was used as a marker to verify grafting and to estimate the grafting efficiency by ESCA analysis. Tapping modesp{TM} atomic force microscopy (TMAFM) images of the grafted fibers revealed a nodular surface topography with dimensions that were correlated to the surface conformation of the grafts using a 'hard-sphere' model. Finally, three styrene/acrylonitrile/butyl acrylate interphases, each with a different copolymer composition, were grafted to evaluate the effect of interphase mechanics on the reinforcing and impact properties of woven-fiber-reinforced, three-phase composites. Accordingly, the interfacial and composite properties were tailored by varying the graft composition as well as the grafting efficiency. Moreover, the grafted interphases elicited a synergistic response in terms of the reinforcement and impact properties, a result previously unobtainable by oxidative-type surface treatments.

Arnold, Jesse Judson

1997-11-01

200

Measurements of the Radiation Induced Conductivity of Insulating Polymeric Materials for the James Webb Space Telescope  

Microsoft Academic Search

We report on initial measurements of Radiation Induced Conductivity (RIC) for twelve thin film polymer materials that are used in the cabling of the James Webb Space Telescope. Results will be used to model possible detrimental arching due to space craft charging effects. RIC occurs when incident ionizing radiation deposits energy in a material and excites electrons into the conduction

J. Corbridge; J. R. Dennison; J. Hodges; R. C. Hoffmann; J. Abbott; A. Hunt; R. Spaulding

2006-01-01

201

Grafting of styrene onto carbon fiber having perester groups  

Microsoft Academic Search

The oxidized carbon fiber having t-butyl perester groups was prepared by the esterification of acid chloride groups on the carbon fiber with t-butyl hydroperoxide. Then, graft polymerization of styrene onto the carbon fiber having t-butyl perester group was carried out. The concentration of monomer affected grafting efficiency. The grafting efficiency increases with the polymerization time and reachs a constant value

Ryutoku Yosomiya; Takao Fujisawa

1985-01-01

202

Investigation of space radiation effects in polymeric film-forming materials  

NASA Technical Reports Server (NTRS)

The literature search in the field of ultraviolet radiation effects that was conducted during the previous program, Contract No. NAS1-12549, has been expanded to include the effects of charged particle radiation and high energy electromagnetic radiation. The literature from 1958 to 1969 was searched manually, while the literature from 1969 to present was searched by using a computerized keyword system. The information generated from this search was utilized for the design of an experimental program aimed at the development of materials with improved resistance to the vacuum-radiation environment of space. Preliminary irradiation experiments were performed which indicate that the approaches and criteria employed are very promising and may provide a solution to the challenging problem of polymer stability to combined ultraviolet/high energy radiation.

Giori, C.; Yamauchi, T.; Jarke, F.

1975-01-01

203

Radiation-induced and RAFT-mediated grafting of poly(hydroxyethyl methacrylate) (PHEMA) from cellulose surfaces  

NASA Astrophysics Data System (ADS)

This paper presents the results of RAFT mediated free-radical graft copolymerization of 2-hydroxyethyl methacrylate (HEMA) onto cellulose fibers in a "grafting-from" approach under ?-irradiation. The effects of absorbed dose and monomer concentration on the graft ratios were investigated at different monomer (HEMA) to RAFT agent (cumyl dithiobenzoate, CDB) ratios. Cellulose-g-PHEMA copolymers with various graft ratios up to 92% (w/w) have been synthesized. The synthesized copolymers were characterized by ATR-FTIR spectroscopy, X-ray photoelectron spectroscopy, elemental analysis and scanning electron microscopy. The results of various techniques confirmed the existence of PHEMA in the copolymer composition.

Kodama, Yasko; Barsbay, Murat; Güven, Olgun

2014-01-01

204

Chronic graft-versus-host disease in the rat radiation chimera. III. Immunology and immunopathology in rapidly induced models  

SciTech Connect

Although chronic graft-versus-host disease (GVHD) frequently develops in the long-term rat radiation chimera, we present three additional models in which a histologically similar disease is rapidly induced. These include adoptive transfer of spleen and bone marrow from rats with spontaneous chronic GVHD into lethally irradiated rats of the primary host strain; sublethal irradiation of stable chimeras followed by a booster transplant; and transfer of spleen cells of chimeras recovering from acute GVHD into second-party (primary recipient strain) or third-party hosts. Some immunopathologic and immune abnormalities associated with spontaneous chronic GVHD were not observed in one or more of the induced models. Thus, IgM deposition in the skin, antinuclear antibodies, and vasculitis appear to be paraphenomena. On the other hand, lymphoid hypocellularity of the thymic medulla, immaturity of splenic follicles, and nonspecific suppressor cells were consistently present in the long term chimeras, and in all models. These abnormalities therefore may be pathogenetically important, or closely related to the development of chronic GVHD.

Beschorner, W.E.; Tutschka, P.J.; Santos, G.W.

1983-03-01

205

Synthesis of chemically cross-linked polyvinyl alcohol-co-poly (methacrylic acid) hydrogels by copolymerization; a potential graft-polymeric carrier for oral delivery of 5-fluorouracil  

PubMed Central

Background of the Study The propose of the present work was to develop chemically cross-linked polyvinyl alcohol-co-poly(methacrylic acid) hydrogel (PVA-MAA hydrogel) for pH responsive delivery of 5-Fluorouracil (5-FU). Methods PVA based hydrogels were prepared by free radical copolymerization. PVA has been cross-linked chemically with monomer (methacrylic acid) in aqueous medium, cross-linking agent was ethylene glycol di-methacrylate (EGDMA) and benzoyl peroxide was added as reaction initiator. 5-FU was loaded as model drug. FTIR, XRD, TGA and DSC were performed for characterization of copolymer. Surface morphology was studied by SEM. pH sensitive properties were evaluated by swelling dynamics and equilibrium swelling ratio at low and higher pH. Results FTIR, XRD, TGA and DSC studies confirmed the formation of new copolymer. Formulations with higher MAA contents showed maximum swelling at 7.4 pH. High drug loading and higher drug release has been observed at pH 7.4. Conclusions The current study concludes that a stable copolymeric network of PVA was developed with MAA. The prepared hydrogels were highly pH responsive. This polymeric network could be a potential delivery system for colon targeting of 5-FU in colorectal cancers. PMID:23721569

2013-01-01

206

Synthesis and characterization of photoluminescent hybrids of poly( ?-caprolactone)-grafted-polyhedral oligosilsesquioxane by using a combination of ring-opening polymerization and click chemistry  

NASA Astrophysics Data System (ADS)

Photoluminescent hybrids of poly( ?-caprolactone) (PCL), polyhedral oligosilsesquioxane (POSS) and terbium ions (Tb3+) were synthesized by using a combination of ring-opening polymerization (ROP), click chemistry and coordination chemistry. Initially, acetylene functionalized PCL (alkyne-PCL-COOH) was prepared by using ROP of ?-caprolactone with propargyl alcohol, and azide-substituted POSS (POSS-N3) was prepared by using the reaction of chloropropyl-heptaisobutyl-substituted POSS with NaN3. The click reaction between alkyne-PCL-COOH and POSS-N3 afforded POSS-g-PCL, which was subsequently coordinated with Tb3+ ions in the presence of 1,10-phenanthroline to produce POSS-g-PCL-Tb3+-Phen. The structures and compositions of the hybrids were investigated by using 1H nuclear magnetic resonance (NMR), Fourier-transform infrared spectroscopy (FT-IR), Field emission scanning electron microscope (FE-SEM), Transmission electron microscopy (TEM), and Thermogravimetric analysis (TGA). The optical properties of POSS-g-PCL-Tb3+-Phen complexes were characterized by using photoluminescence spectroscopy, which showed four high emission bands centered at 489, 545, 584, and 620 nm with excitation at 330 nm. The emission spectra of the europium-ion-coordinated hybrids, POSS-g-PCL-Eu3+-Phen, had four high-intensity peaks, 594, 617, 652 and 686 nm, for an excitation wavelength of 352 nm.

Cao, Xuan Thang; Showkat, Ali Md; Bach, Long Giang; Jeong, Yeon Tae; Kim, Jong Soo; Lim, Kwon Taek; Gal, Yeong-Soon

2015-01-01

207

Flash polymerization of silicone oils using gamma radiation for conserving waterlogged wood  

E-print Network

the SFD-I /SFD-5 mix. These bulked samples were exposed to gamma radiation emitted from a nuclear research reactor and received gamma doses ranging from 30 Gy to 228 Gy with dose rates ranging from 0.6 Gy/min to 5.1 Gy/min. Following irradiation, thin...

Gidden, Richmond Paul

1996-01-01

208

Radiation grafting of N,N?-dimethylacrylamide and N-isopropylacrylamide onto polypropylene films by two-step method  

NASA Astrophysics Data System (ADS)

Polypropylene (PP) films were modified by the consecutive grafting of N,N'-dimethylacrylamide (DMAAm) and N-isopropylacrylamide (NIPAAm) (two-step method) using preirradiation method with gamma-rays. The effect of absorbed dose, monomer concentration and reaction time on the degree of grafting was determined. The grafted samples were verified by the FTIR-ATR spectroscopy; thermal properties were analyzed by differential scanning calorimetry (DSC) and the stimuli-responsive behavior was studied by swelling and contact angle in water as well as DSC. Thermoresponsive films of (PP- g-DMAAm)- g-NIPAAm presented a lower critical solution temperature (LCST) at 36.5 °C.

Contreras-García, A.; Burillo, G.; Aliev, R.; Bucio, E.

2008-08-01

209

Thermo-responsive behavior of a methacryloyl-DL-alanine methyl ester polymer gel prepared by radiation-induced polymerization  

NASA Astrophysics Data System (ADS)

Loosely cross-linked poly(methacryloyl- DL-alanine methyl ester, MA- DL-AlaOme) gels, which were prepared by radiation-induced polymerization, exhibited a reversible low-temperature swelling and high-temperature deswelling when cycled in water at different temperatures at 24-h intervals, in the range of 0 and 40°C. The thermo-response strongly depended upon irradiation condition. Increasing the irradiation dose resulted in a formation of lower molecular weight polymer owing to the scission of polymer chain, in which it gave a high swelling ability at low temperature, in contrast to a sluggish shrinkage at high temperature. On the other hand, no irradiation temperature affects the thermo-response of the gel. An important characteristic of the MA- DL-AlaOMe polymer gel is the formation of the membrane barrier at the surface with the rise in temperature, but it disappears in reswelling, to be termed "surface-controlling on-off switch system". Brilliant blue FCF (BB) as a model compound was corporated into the gel to evaluate the capability as a thermo-responsive carrier for application in drug delivery systems, and it was found that the reversibly surface-controlling on-off switch function responsible to temperature changes plays an important role in a pulsatile release of BB of BB from the gel in vivo.

Ding, Zhong-Li; Yoshida, Masaru; Asano, Masaharu; Ma, Zue-Teh; Omichi, Hideki; Katakai, Ryoichi

1994-09-01

210

Plant grafting.  

PubMed

Since ancient times, people have cut and joined together plants of different varieties or species so they would grow as a single plant - a process known as grafting (Figures 1 and 2). References to grafting appear in the Bible, ancient Greek and ancient Chinese texts, indicating that grafting was practised in Europe, the Middle East and Asia by at least the 5(th) century BCE. It is unknown where or how grafting was first discovered, but it is likely that natural grafting, the process by which two plants touch and fuse limbs or roots in the absence of human interference (Figure 3), influenced people's thinking. Such natural grafts are generally uncommon, but are seen in certain species, including English ivy. Parasitic plants, such as mistletoe, that grow and feed on often unrelated species may have also contributed to the development of grafting as a technique, as people would have observed mistletoe growing on trees such as apples or poplars. PMID:25734263

Melnyk, Charles W; Meyerowitz, Elliot M

2015-03-01

211

The effect of nanocomposite polymeric layer on the radiation of antisymmetric zero-order Lamb wave in a piezoelectric plate contacting with liquid  

NASA Astrophysics Data System (ADS)

A nanocomposite polymeric layer is proposed to be used for increasing the efficiency of ultrasound radiation into the liquid by antisymmetric zero-order (A0) Lamb waves propagating in piezoelectric plates. The theoretical and experimental investigations of the influence of the nanocomposite polymeric layers on the efficiency and radiation angle of acoustic wave into liquid were carried out. It has been theoretically shown that the use of the layer of the polyethylene of low density with nanoparticles of cadmium sulfide of concentration 25% between the plate of 128YX LiNbO3 and water medium allows to increase the radiation attenuation on ˜1 dB/? if the ratio of the thicknesses of the layer and plate is equal to 0.16 at the frequency of 1.3 MHz. The experimental data were in a good agreement with theoretical results. It has been also shown that the presence of nanocomposite film leads to the increase of the radiation angle of bulk acoustic wave in liquid and allows the effective operation of the radiator not only in the sweet water but also in salt one. The obtained results may be used for the development of effective radiators/receivers of acoustic waves in liquids for flow meters and for underwater communication systems.

Kuznetsova, I. E.; Zaitsev, B. D.; Borodina, I. A.; Shikhabudinov, A. M.; Teplykh, A. A.; Manga, E.; Feuillard, G.

2013-06-01

212

Temperature-responsiveness and biocompatibility of DEGMA/OEGMA radiation-grafted onto PP and LDPE films  

NASA Astrophysics Data System (ADS)

Polypropylene (PP) and low density polyethylene (LDPE) were modified by ?-ray grafting of di(ethylene glycol) methyl ether methacrylate (DEGMA) and oligo (ethylene glycol) methyl ether methacrylate (OEGMA300 or OEGMA475 with Mn 300 and 475 respectively) with different monomer concentrations and mol ratios. The grafting percentage was evaluated as a function of the solvent, irradiation dose, reaction time, temperature, and monomers concentration. The grafted materials were more hydrophilic than the pristine polymers, as observed by contact angle and swelling in water. Temperature-responsive behavior was evaluated using DSC showing transitions between 34 and 48 °C. In vitro hemocompatibility, protein adsorption, cytotoxicity and bacteria adhesion tests were also carried out. Overall, the DEGMA/OEGMA grafting provides hemo and cytocompatible materials that exhibit temperature-responsive hydrophilic features and decreased protein adsorption.

Ramírez-Jiménez, Alejandro; Alvarez-Lorenzo, Carmen; Concheiro, Angel; Bucio, Emilio

2014-06-01

213

Radiation-induced polymerization of cyclophosphazene trimers. Final report, 1 September 1985-30 September 1988  

SciTech Connect

Hexachlorophosphazene was irradiated in bulk and in solution after various methods of purification. When rigorously dried and purified, good yields of polymer were obtained. Poor reproducibility was found in the bulk but reasonably good results were obtained in decalin solution. The best yields and highest molecular weights were obtained after the addition of small amounts of the bulky electron acceptor pyromellitic dianhydride. Hexachlorocyclotriphosphazene was purified by recrystallization for various times from dried heptane. The trimer was then further purified by repeated sublimation steps under high vacuum. Finally the trimer was dried in the melt over rigorously baked out barium oxide. The monomer was then transferred to ampules or the NMR tubes for radiation and subsequent determination of the polymer content.

Stannett, V.T.

1989-01-04

214

Polymeric microspheres  

DOEpatents

The invention features core-shell microsphere compositions, hollow polymeric microspheres, and methods for making the microspheres. The microspheres are characterized as having a polymeric shell with consistent shell thickness.

Walt, David R.; Mandal, Tarun K.; Fleming, Michael S.

2004-04-13

215

Radiation synthesis of multifunctional polymeric hydrogels for oral delivery of insulin.  

PubMed

Polyelectrolyte crosslinked hydrogel was synthesized using gamma radiation-induced copolymerization of methacrylic acid (MAA), N,N-dimethyl aminoethyl methacrylate (DMAEMA) in aqueous solution to utilize for oral delivery of insulin. The influence of copolymer composition and pH value of the surrounding medium on the type of water diffusion in the glassy polymer was discussed. In addition, the swelling kinetics tests on MAA/DMAEMA (90/10) reveal that the swelling kinetics of the proposed hydrogel follows a Fickian diffusion process in media of pH 5, and an anomalous diffusion process in media of pH 1.5 and 7.2. The cross-linked three-dimensional polymers were characterized by scanning electron microscopy and FT-IR. In the matrices with increase in the content of MAA had shown increased bioadhesivity. Insulin was entrapped in these gels and the in vitro release profiles were established separately in both (SGF, pH 1.5) and (SIF, pH 7.2). The release profile of insulin showed negligible release in acidic media (SGF, pH 1.5) and sustained release in simulated intestinal fluid (SIF, pH 7.2). Drug release studies showed that the increasing content of MAA in the copolymer enhances release in SIF to design and improve insulin release behavior from these carriers. PMID:24055698

Abou Taleb, Manal F

2013-11-01

216

Preparation of a new micro-porous poly(methyl methacrylate)-grafted polyethylene separator for high performance Li secondary battery  

NASA Astrophysics Data System (ADS)

In this study, micro-porous poly(methyl methacrylate)-grafted polyethylene separators (PE-g-PMMA) were prepared by a radiation-induced graft polymerization of methyl methacrylate onto a conventional PE separator followed by a phase inversion. After the phase inversion, the micro-pores were generated in the grafted PMMA layer. The prepared micro-porous PE-g-PMMA separators showed an improved electrolyte uptake and ionic conductivity due to their improved affinity with a liquid electrolyte and the presence of pores in the grafted PMMA layer. The PE-g-PMMA separators exhibited a lower thermal shrinkage compared to the original PE separator. The PE-g-PMMA separators showed a better oxidation stability up to 5.0 V when compared to the original PE separator (4.5 V).

Gwon, Sung-Jin; Choi, Jae-Hak; Sohn, Joon-Yong; Ihm, Young-Eon; Nho, Young-Chang

2009-10-01

217

Physical properties of agave cellulose graft polymethyl methacrylate  

SciTech Connect

The grafting polymerization of methyl methacrylate and Agave cellulose was prepared and their structural analysis and morphology were investigated. The grafting reaction was carried out in an aqueous medium using ceric ammonium nitrate as an initiator. The structural analysis of the graft copolymers was carried out by Fourier transform infrared and X-ray diffraction. The graft copolymers were also characterized by field emission scanning electron microscopy (FESEM). An additional peak at 1732 cm{sup ?1} which was attributed to the C=O of ester stretching vibration of poly(methyl methacrylate), appeared in the spectrum of grafted Agave cellulose. A slight decrease of crystallinity index upon grafting was found from 0.74 to 0.68 for cellulose and grafted Agave cellulose, respectively. Another evidence of grafting showed in the FESEM observation, where the surface of the grafted cellulose was found to be roughed than the raw one.

Rosli, Noor Afizah; Ahmad, Ishak; Abdullah, Ibrahim; Anuar, Farah Hannan [Polymer Research Centre (PORCE), School of Chemical Sciences and Food Technology, Faculty of Science and Technology, Universiti Kebangsaan Malaysia, 43600 Bangi Selangor (Malaysia)

2013-11-27

218

Physical properties of agave cellulose graft polymethyl methacrylate  

NASA Astrophysics Data System (ADS)

The grafting polymerization of methyl methacrylate and Agave cellulose was prepared and their structural analysis and morphology were investigated. The grafting reaction was carried out in an aqueous medium using ceric ammonium nitrate as an initiator. The structural analysis of the graft copolymers was carried out by Fourier transform infrared and X-ray diffraction. The graft copolymers were also characterized by field emission scanning electron microscopy (FESEM). An additional peak at 1732 cm-1 which was attributed to the C=O of ester stretching vibration of poly(methyl methacrylate), appeared in the spectrum of grafted Agave cellulose. A slight decrease of crystallinity index upon grafting was found from 0.74 to 0.68 for cellulose and grafted Agave cellulose, respectively. Another evidence of grafting showed in the FESEM observation, where the surface of the grafted cellulose was found to be roughed than the raw one.

Rosli, Noor Afizah; Ahmad, Ishak; Abdullah, Ibrahim; Anuar, Farah Hannan

2013-11-01

219

Uranium Recovery from Seawater: Development of Fiber Adsorbents Prepared via Atom-Transfer Radical Polymerization  

SciTech Connect

A novel adsorbent preparation method using atom-transfer radical polymerization (ATRP) combined with radiation-induced graft polymerization (RIGP) was developed to synthesize an adsorbent for uranium recovery from seawater. The ATRP method allowed a much higher degree of grafting on the adsorbent fibers (595 2818%) than that allowed by RIGP alone. The adsorbents were prepared with varied composition of amidoxime groups and hydrophilic acrylate groups. The successful preparation revealed that both ligand density and hydrophilicity were critical for optimal performance of the adsorbents. Adsorbents synthesized in this study showed a relatively high performance (141 179 mg/g at 49 62 % adsorption) in laboratory screening tests using a uranium concentration of ~6 ppm. This performance is much higher than that of known commercial adsorbents. However, actual seawater experiment showed impeded performance compared to the recently reported high-surface-area-fiber adsorbents, due to slow adsorption kinetics. The impeded performance motivated an investigation of the effect of hydrophilic block addition on the graft chain terminus. The addition of hydrophilic block on the graft chain terminus nearly doubled the uranium adsorption capacity in seawater, from 1.56 mg/g to 3.02 mg/g. The investigation revealed the importance of polymer chain conformation, in addition to ligand and hydrophilic group ratio, for advanced adsorbent synthesis for uranium recovery from seawater.

Saito, Tomonori [ORNL; Brown, Suree [ORNL; Chatterjee, Sabornie [ORNL; Kim, Jungseung [ORNL; Tsouris, Costas [ORNL; Mayes, Richard T [ORNL; Kuo, Li-Jung [Pacific Northwest National Laboratory (PNNL); Gill, Gary [Pacific Northwest National Laboratory (PNNL); Oyola, Yatsandra [ORNL; Janke, Christopher James [ORNL; Dai, Sheng [ORNL

2014-01-01

220

PP films grafted with N-isopropylacrylamide and N-(3-aminopropyl) methacrylamide by ? radiation: synthesis and characterization  

NASA Astrophysics Data System (ADS)

Simultaneous grafting of N-isopropylacrylamide (NIPAAm) and N-(3-aminopropyl) methacrylamide hydrochloride (APMA) on polypropylene (PP) was investigated for obtaining interfaces that are stimuli-responsive under physiological conditions. A pre-irradiation method was optimized tuning the ?-irradiation dose, reaction time, temperature, and monomers concentrations. FT-IR ATR and XPS analysis of the grafted copolymers evidenced a greater content in NIPAAm than in APMA; the APMA/NIPAAm ratio increasing with the concentration of APMA in the reaction medium and when the grafting was carried out in 1 M NaNO 3. The grafted films were characterized regarding their thermal properties (DSC and TGA) swelling behavior and contact angle. Immersion of the pre-irradiated films in 1 M NIPAAm/0.5 M APMA aqueous solution rendered PP-g-(1NIPAAm- r-0.5APMA) which exhibited rapid and reversible transitions showing a LCST around the physiological temperature. By contrast, a greater content in APMA enhanced the hydrophilicity and prevented the shrinking of PP-g-(1NIPAAm- r-1APMA).

Contreras-García, Angel; Alvarez-Lorenzo, Carmen; Concheiro, Angel; Bucio, Emilio

2010-05-01

221

Impact of reaction conditions on grafting acrylamide onto starch  

Technology Transfer Automated Retrieval System (TEKTRAN)

We have explored the radical initiated graft polymerization reaction of acrylamide onto starch where the solvent, concentration, temperature and reaction times were varied. We have found that the morphology of the resulting grafted polymer is dramatically different and is dependent on the reaction c...

222

Graft-copolymerization of PVC with polymerizable UV absorbers  

Microsoft Academic Search

Polyvlnyl chloride has been grafted with two different monofunctional polymerizable ultraviolet (UV) absorbers, 4-methacryloyloxy-2-hydroxybenzophenone and 2(2-hydroxy-4-methacryloyloxyphenyl) 2H-5-methoxy-benzotriazole. PVC was activated by dehydrochlorinating it in pyridine and subsequently grafted with the monomeric UV absorbers in tetrahydrofuran by free radical polymerization. The molar masses of the resulting grafted polymers and the distribution of the UV absorber moleties along different molar mass fractions

A. Al-Mobasher; S. Attari; H. Pasch; K. F. Shuhaibar; F. A. Rasoul

1991-01-01

223

Synthesis and characterization of radiation grafted films for removal of arsenic and some heavy metals from contaminated water  

NASA Astrophysics Data System (ADS)

Grafting of styrene/maleic anhydride and methyl methacrylate/maleic anhydride binary monomers onto the low density polyethylene film was performed using the ?-ray irradiation technique. Then, the synthesized grafted films were treated with different ammonia derivatives for developing chelating functionalization. These chelating products were characterized by the gravimetric method as well as by the Fourier transformed infrared spectroscopic method, and were used for removal of arsenic and some heavy metals from aqueous solutions. The optimum absorbed dose of 30 kGy reveals the graft yielding of about 325% in the films. Uptake of arsenic and some heavy-metal ions (Cr(III), Mn(II), Fe(III), Ni(II), Cu(II) and Pb(II)) from contaminated water by the chelating functionalized films (CFF) was examined by an atomic absorption spectrophotometer. The maximum arsenic removal capacity of 5062 mg/kg has been observed for the film treated with hydroxylamine hydrochloride. The CFF prepared by semicarbazide and thiol analogs show affinity toward the metal ions with an order: Cu(II)>Fe(III)>Mn(II) etc. The results obtained from this study indicate that the functionalized films show good chelating and ion-exchange property for metal ions.

Chowdhury, M. N. K.; Khan, M. W.; Mina, M. F.; Beg, M. D. H.; Khan, Maksudur R.; Alam, A. K. M. M.

2012-10-01

224

Structure-function properties of starch spherulites grafted with poly(methyl acrylate)  

Technology Transfer Automated Retrieval System (TEKTRAN)

Spherulites, produced by steam jet-cooking high-amylose starch and oleic acid, were grafted with methyl acrylate, both before and after removal of un-complexed amylopectin. For comparison, granular high-amylose corn starch was graft polymerized in a similar manner. The amount of grafted and ungrafte...

225

Production of monodisperse, polymeric microspheres  

NASA Technical Reports Server (NTRS)

Very small, individual polymeric microspheres with very precise size and a wide variation in monomer type and properties are produced by deploying a precisely formed liquid monomer droplet, suitably an acrylic compound such as hydroxyethyl methacrylate into a containerless environment. The droplet which assumes a spheroid shape is subjected to polymerizing radiation such as ultraviolet or gamma radiation as it travels through the environment. Polymeric microspheres having precise diameters varying no more than plus or minus 5 percent from an average size are recovered. Many types of fillers including magnetic fillers may be dispersed in the liquid droplet.

Rembaum, Alan (Inventor); Rhim, Won-Kyu (Inventor); Hyson, Michael T. (Inventor); Chang, Manchium (Inventor)

1990-01-01

226

Polymerization and surface modification by low pressure plasma technique  

NASA Astrophysics Data System (ADS)

A durable water repellent, stain resistant or flame retardant character can be conferred to polyacrylonitrile (PAN) textiles by using the plasma induced graft polymerization technique. The monomers used are perfluoroalkylacrylate, (meth)acrylate phosphates, and phosphonates which are well known to be effective for the waterproofing and the fireproofing of polymeric substrates, respectively.

Tsafack, M.-J.; Hochart, F.; Levalois-Grützmacher, J.

2004-06-01

227

Laundering durable antibacterial cotton fabrics grafted with pomegranate-shaped polymer wrapped in silver nanoparticle aggregations  

PubMed Central

To improve the laundering durability of the silver functionalized antibacterial cotton fabrics, a radiation-induced coincident reduction and graft polymerization is reported herein where a pomegranate-shaped silver nanoparticle aggregations up to 500?nm can be formed due to the coordination forces between amino group and silver and the wrapping procedure originated from the coincident growth of the silver nanoparticles and polymer graft chains. This pomegranate-shaped silver NPAs functionalized cotton fabric exhibits outstanding antibacterial activities and also excellent laundering durability, where it can inactivate higher than 90% of both E. coli and S. aureus even after 50 accelerated laundering cycles, which is equivalent to 250 commercial or domestic laundering cycles. PMID:25082297

Liu, Hanzhou; Lv, Ming; Deng, Bo; Li, Jingye; Yu, Ming; Huang, Qing; Fan, Chunhai

2014-01-01

228

Laundering durable antibacterial cotton fabrics grafted with pomegranate-shaped polymer wrapped in silver nanoparticle aggregations  

NASA Astrophysics Data System (ADS)

To improve the laundering durability of the silver functionalized antibacterial cotton fabrics, a radiation-induced coincident reduction and graft polymerization is reported herein where a pomegranate-shaped silver nanoparticle aggregations up to 500 nm can be formed due to the coordination forces between amino group and silver and the wrapping procedure originated from the coincident growth of the silver nanoparticles and polymer graft chains. This pomegranate-shaped silver NPAs functionalized cotton fabric exhibits outstanding antibacterial activities and also excellent laundering durability, where it can inactivate higher than 90% of both E. coli and S. aureus even after 50 accelerated laundering cycles, which is equivalent to 250 commercial or domestic laundering cycles.

Liu, Hanzhou; Lv, Ming; Deng, Bo; Li, Jingye; Yu, Ming; Huang, Qing; Fan, Chunhai

2014-08-01

229

Graft copolymers from poly(2,6-dimethylphenylene oxide) and pivalolactone  

NASA Technical Reports Server (NTRS)

The copolyether-polyester system resulting from the anionic graft polymerization of pivalolactone onto poly(2,6-dimethylphenylene oxide) has been formulated with differing graft densities and graft segment lengths. Wide angle X-ray scattering studies on these materials indicated an increased crystalline order with increased PVL segments/graft for similarly annealed specimens and a decrease in such order with increasing carboxylation.

Bell, Vernon L.; Wakelyn, N. T.

1988-01-01

230

Radiation-induced polymerization of 2,3-dimethyl-1,3-butadiene clathrate in deoxycholic acid  

Microsoft Academic Search

Poly(dimethylbutadiene) (PDMB) was synthesized through the inclusion polymerization technique, by ?-irradiation of a clathrate\\u000a of 2,3-dimethyl-1,3-butadiene in deoxycholic acid (DOCA) at 75, 150, 320 and 430 kGy. The resulting inclusion complexes PDMB@DOCA\\u000a were studied by FTIR spectroscopy and by thermal analysis (DTA, TGA and DTG). Pure PDMB was isolated by extracting the complex\\u000a PDMB@DOCA with ethanol. The best sample in

F. Cataldo; O. Ursini; P. Ragni; A. Rosati

2009-01-01

231

Surface Modification of PET Fabric by Graft Copolymerization with Acrylic Acid and Its Antibacterial Properties  

PubMed Central

Graft copolymerization of acrylic acid (AA) onto Poly(ethylene terephthalate) (PET) fabrics with the aid of benzoyl peroxide was carried out. The effect of polymerization parameters on the graft yield was studied. Percent grafting was enhanced significantly by increasing benzoyl peroxide (BP) concentrations up to 3.84?g/lit and then decreased upon further increase in initiator concentration. Preswelling of PET leads to changes in its sorption-diffusion properties and favors an increase in the degree of grafting. The antibiotics treated grafted fabrics showed antibacterial properties towards gram-positive and gram-negative microorganisms. FTIR and SEM were used to characterize AA-grafted polyester fabrics. PMID:24052819

Abdolahifard, M.; Bahrami, S. Hajir; Malek, R. M. A.

2011-01-01

232

Location and size of nanoscale free-volume holes in crosslinked- polytetrafluoroethylene-based graft-type polymer electrolyte membranes determined by positron annihilation lifetime spectroscopy  

NASA Astrophysics Data System (ADS)

The location and size of nanoscale free-volume holes (nanoholes) in graft-type polymer electrolyte membranes (PEMs), which were prepared by radiation-induced graft polymerization (grafting) of styrene into crosslinked-polytetrafluoroethylene (cPTFE) films and subsequent sulfonation, were investigated using positron annihilation lifetime (PAL) spectroscopy. The PAL spectra of the PEMs indicated the existence of two types of ortho-positronium (o-Ps) species, corresponding to nanoholes with volumes of 0.11 and 0.38 nm3. A comparison of the PAL data of the PEMs with that of the precursor original cPTFE and polystyrene-grafted films demonstrated the probability that the smaller holes were located in both the PTFE crystalline phases and the poly(styrene sulfonic acid) graft regions, whereas the larger holes are potentially localized in the PTFE amorphous phases. Taking into account both the size and the location of the nanoholes, it was concluded that gas transport through the larger holes in the amorphous PTFE phases was dominant over permeation through the smaller holes in the PTFE crystals and grafted regions.

Sawada, Shin-ichi; Yabuuchi, Atsushi; Maekawa, Masaki; Kawasuso, Atsuo; Maekawa, Yasunari

2013-06-01

233

Polymeric nanoparticles  

PubMed Central

Nanocarriers with various compositions and biological properties have been extensively applied for in vitro/in vivo drug and gene delivery. The family of nanocarriers includes polymeric nanoparticles, lipid-based carriers (liposomes/micelles), dendrimers, carbon nanotubes, and gold nanoparticles (nanoshells/nanocages). Among different delivery systems, polymeric carriers have several properties such as: easy to synthesize, inexpensive, biocompatible, biodegradable, non-immunogenic, non-toxic, and water soluble. In addition, cationic polymers seem to produce more stable complexes led to a more protection during cellular trafficking than cationic lipids. Nanoparticles often show significant adjuvant effects in vaccine delivery since they may be easily taken up by antigen presenting cells (APCs). Natural polymers such as polysaccharides and synthetic polymers have demonstrated great potential to form vaccine nanoparticles. The development of new adjuvants or delivery systems for DNA and protein immunization is an expanding research field. This review describes polymeric carriers especially PLGA, chitosan, and PEI as vaccine delivery systems. PMID:24128651

Bolhassani, Azam; Javanzad, Shabnam; Saleh, Tayebeh; Hashemi, Mehrdad; Aghasadeghi, Mohammad Reza; Sadat, Seyed Mehdi

2014-01-01

234

Structure-function properties of amylose-oleic acid inclusion complexes grafted with poly(methyl acrylate)  

Technology Transfer Automated Retrieval System (TEKTRAN)

Spherulites, produced by steam jet-cooking high-amylose starch and oleic acid, were grafted with methyl acrylate, both before and after removal of un-complexed amylopectin. For comparison, granular high-amylose corn starch was graft polymerized in a similar manner. The amount of grafted and ungrafte...

235

Synthesis of graft polyrotaxane by simultaneous capping of backbone and grafting from rings of pseudo-polyrotaxane  

PubMed Central

Summary Graft polyrotaxanes, with poly(?-caprolactone) (PCL) graft chains on the ring components were synthesized by the simultaneous ring-opening polymerization of ?-caprolactone from both ends of the backbone polymer, an end-functionalized polyethylene glycol (PEG) and the formation of inclusion complexes with ?-cyclodextrin (?-CD). PEG with multiple functional groups at each end was prepared by the condensation of PEG-amine and D-gluconic acid; the PEG derivative formed an inclusion complex with ?-CD. The polymerization of multiple hydroxy groups at the backbone ends resulted in a star-shaped end group, which served as a bulky capping group to prevent dethreading. In contrast, PEG with only one hydroxy group at each end did not produce polyrotaxanes, indicating that single PCL chains were too thin to confine ?-CDs to the complex. In addition, the grafting polymerization proceeded properly only when robust hydrogen bonds formed between ?-CDs were dissociated using a basic catalyst. Since the dissociation also induced dethreading, kinetic control of the polymerization and dissociation were crucial for producing graft polyrotaxanes. Consequently, this three-step reaction yielded graft polyrotaxanes in a good yield, demonstrating a significant simplification of the synthesis of graft polyrotaxanes. PMID:25383129

Inoue, Katsunari; Kudo, Masabumi

2014-01-01

236

Synthesis of graft polyrotaxane by simultaneous capping of backbone and grafting from rings of pseudo-polyrotaxane.  

PubMed

Graft polyrotaxanes, with poly(?-caprolactone) (PCL) graft chains on the ring components were synthesized by the simultaneous ring-opening polymerization of ?-caprolactone from both ends of the backbone polymer, an end-functionalized polyethylene glycol (PEG) and the formation of inclusion complexes with ?-cyclodextrin (?-CD). PEG with multiple functional groups at each end was prepared by the condensation of PEG-amine and D-gluconic acid; the PEG derivative formed an inclusion complex with ?-CD. The polymerization of multiple hydroxy groups at the backbone ends resulted in a star-shaped end group, which served as a bulky capping group to prevent dethreading. In contrast, PEG with only one hydroxy group at each end did not produce polyrotaxanes, indicating that single PCL chains were too thin to confine ?-CDs to the complex. In addition, the grafting polymerization proceeded properly only when robust hydrogen bonds formed between ?-CDs were dissociated using a basic catalyst. Since the dissociation also induced dethreading, kinetic control of the polymerization and dissociation were crucial for producing graft polyrotaxanes. Consequently, this three-step reaction yielded graft polyrotaxanes in a good yield, demonstrating a significant simplification of the synthesis of graft polyrotaxanes. PMID:25383129

Kato, Kazuaki; Inoue, Katsunari; Kudo, Masabumi; Ito, Kohzo

2014-01-01

237

Cationic Polymerization of N-Vinylcarbazole and N-Vinyl-2Pyrrolidone Initiated by Carboxyl Groups on Carbon Fibers  

Microsoft Academic Search

The effects of solvent and temperature on the grafting of poly(N-vinylcarbazole) (NVC) onto carbon fiber by cationic polymerization initiated by carboxyl groups on the surface were investigated in order to obtain poly-NVC-grafted carbon fiber with a higher percentage of grafting It was found that the rate of the polymerization of NVC increased, depending on the dielectric constant of the solvent,

Norio Tsubokawa; Hiroshi Maruyama; Yasuo Sone

1988-01-01

238

Effects of high energy simulated space radiation on polymeric second-surface mirrors. [thermal control coatings - performance tests  

NASA Technical Reports Server (NTRS)

A radiation effects experimental program was performed, in which second surface mirror type thermal control coatings were exposed to ultraviolet radiation, electrons, and protons simultaneously. Stability was assessed by making periodic spectral reflectance measurements in situ (and in air after testing for comparison). Solar absorption coefficients were derived by computer. Many of the exposed materials showed large amounts of degradation in reflectance absorptance, principally due to the electron exposure. A series of tests was conducted, leading to the identification of a modified second surface mirror that shows considerable improvement and promise for stability during thermal control applications in a charged particle space radiation environment.

Eogdall, L. B.; Cannaday, S. S.

1975-01-01

239

Amphoteric ion exchange membrane synthesized by radiation-induced graft copolymerization of styrene and dimethylaminoethyl methacrylate into PVDF film for vanadium redox flow battery applications  

Microsoft Academic Search

Poly(vinylidene difluoride) (PVDF) film was grafted with styrene (St) and dimethylaminoethyl methacrylate (DMAEMA) using ?-irradiation techniques. Through subsequent sulfonation and protonation processes, a new kind of amphoteric ion exchange membrane (AIEM) was synthesized. The grafting yield (GY) increased with absorbed dose and leveled off at about 60kGy. The composition of poly(St-co-DMAEMA) grafts was correlated to the ratio of St to

Jingyi Qiu; Junzhi Zhang; Jinhua Chen; Jing Peng; Ling Xu; Maolin Zhai; Jiuqiang Li; Genshuan Wei

2009-01-01

240

Viability of porcine nasal septal cartilage grafts following Nd:YAG (n=1.32?m) laser radiation  

NASA Astrophysics Data System (ADS)

Mechanically deformed morphologic cartilage grafts undergo a temperature dependent phase transformation during sustained laser irradiation that results in reshaping of the specimen. While thermal, optical, and mechanical properties of cartilage undergoing laser heating have been previously investigated, the viability of these irradiated grafts has yet to be examined closely until now. In this study, chondrocyte viability following laser irradiation was determined by measuring the incorporation of radiolabelled sulfate (Na 35SO4-2) into proteoglycan (PTG) macromolecules. Proteoglycans are highly sulfated and are the principal molecular constituents of cartilage matrix. Their synthesis directly reflects chondrocyte viability. By measuring the scintillation counts of 35SO4-2 uptake and normalizing the value by the total protein content of each specimen we can determine the level of PTG synthesis rates following laser reshaping. Regional baseline PTG synthesis rates as a function of location was determined by dividing each specimen into six regions. All regions except the most cephalic are demonstrated similar PTG synthesis rates. The most cephalic region exhibited a significantly greater PTG synthesis rates. In order to establish a positive control for this study, specimens were immersed in boiling saline water for approximately 40 minutes. The boiled specimens demonstrated a fivefold increase in normalized radioisotope uptake and suggest that the non-specific uptake of radioactive Na35SO4-2 is caused by structural alterations in the collagen matrix caused by extensive thermal exposure. To avoid this thermal artifact, another positive control was established using nitric oxide was to induce apoptosis of the chondrocytes, resulting in significantly lower PTG synthesis compared to untreated tissue. Cartilage specimens (25 X 10 X 2 mm) were irradiated with light emitted from an Nd:YAG laser (25 W/cm2, (lambda) equals 1.32 micrometer) while radiometric surface temperature, internal stress, and backscattered light were simultaneously recorded. Individual specimens underwent either one, two, or three sequential laser exposures with the duration of each exposure determined in real-time from observation of characteristic changes in integrated backscattered light intensity that correlate with thermal mediated stress relaxation. A five-minute time interval between each irradiation was given to allow the cartilage to return to thermal equilibrium. Average laser exposure for each irradiation sequence was recorded (5, 8.3, 12.2 sec). PTG synthesis decreased with increasing laser exposure, but was noted to remain above baseline levels for NO treated tissue. To further refine these results and minimize the effect of regional tissue variations, 7 mm diameter discs excised from the most cephalic portions and a middle region of the pig nasal septal cartilages were irradiated. A reduction of PTG synthesis rates was noted with each successive irradiation, suggesting that laser mediated cartilage reshaping acutely does not eliminate the population of viable chondrocytes. The degree of reduction in PTG synthesis is dependent upon the time-temperature dependent heating profile created during laser irradiation, and carefully monitored dosimetry is necessary to ensure chondrocyte viability.

Chao, Kenneth K. H.; Wong, Brian J.; Kim, Hong K.; Milner, Thomas E.; Sung, Chung-Ho; Sobol, Emil N.; Nelson, J. Stuart

2000-06-01

241

Preparation and characterization of Fe(III)-loaded iminodiacetic acid modified GMA grafted nonwoven fabric adsorbent for anion adsorption  

NASA Astrophysics Data System (ADS)

An Fe(III)-loaded chelating fabric with iminodiacetic acid (IDA) functional groups was prepared by radiation induced graft polymerization of an epoxy group containing monomer, glycidyl methacrylate, onto a nonwoven fabric made of polypropylene coated by polyethylene (PE/PP) and subsequent Fe(III) loading. Grafting conditions were optimized, and GMA grafted polymer was modified with iminodiacetic acid in isopropyl alcohol/water at 80 °C. In order to prepare the polymeric ligand exchanger (PLE) for the removal of phosphate, IDA fabrics were loaded with Fe(III) ions. Fe(III) loading capacity of IDA fabric was determined to be 2.83 mmol Fe(III)/g of polymer. For removal of phosphate anion, adsorption experiments were performed in batch mode at different pH (2-9) and phosphate concentrations. It was found that phosphate adsorption by the Fe(III)-loaded IDA fabric is maximum at pH 2.00. The effect of initial concentration of phosphate on the adsorption behaviour of Fe(III)-loaded IDA nonwoven fabric was determined at low phosphate concentrations (0.5-25 ppm) and at high phosphate concentrations (50-1000 ppm).

Kavakl?, P?nar Akka?; Kavakl?, Cengiz; Güven, Olgun

2014-01-01

242

Radiation-induced mouse chimeras: a cellular analysis of the major lymphoid compartments, factors affecting lethal graft versus host disease and host-tumor interactions  

SciTech Connect

The major lymphoid compartments of allogeneic bone marrow chimeras were evaluated for the extent of cell chimerism and distribution of Thy 1 and la bearing cells. These chimeras contained lymphoid cell primarily of donor origin. The bone marrow compartment was a mixture of host and donor origin cells. The distribution of Thy 1 and la bearing cells was similar as in normal mice. The effect of adult thymectomy alone or followed by whole-body irradiation and bone marrow reconstitution on the distribution of the Thy 1 positive cells was also investigated. Thymectomy with or without WBI and bone marrow reconstitution significantly lowered the number of Thy 1 bearing cells in the blood and spleen. The number of la bearing cells did not appear to be affected by thymectomy. The role of circulating lymphoid cells in the incidence of lethal graft versus host disease (GVHD) in radiation induced fully allogeneic mouse chimeras was studied. Mice reconstituted with allogeneic bone marrow from bled donors had a statistically lower incidence of GVHD than those reconstituted with bone marrow from unbled donors. Addition of mature peripheral lymphocytes from blood to the reconstituting bone marrow cells from bled donors reduplicated the high incidence of lethal GVHD. It was demonstrated that the bone marrow of mice not exsanguinated prior to harvesting of bone marrow contained significant numbers of peripheral contaminating cells in the harvested bone marrow. The role of suppressor cell elimination in resisting tumor growth was investigated using radiation induced mouse chimeras. Local effects of irradiation alone at the site of tumor inoculation could account for this lack of growth.

Almaraz, R.

1981-01-01

243

Self-assembly of amylose-grafted carboxymethyl cellulose.  

PubMed

In this study, we performed the self-assembly of the amylose-grafted carboxymethyl cellulose sodium salt (NaCMC) for the formation of nanofiber films under aqueous conditions. The introduction of amylose graft chains was conducted by the chemoenzymatic approach including phosphorylase-catalyzed enzymatic polymerization. The product had the rigid NaCMC main chain, which further assembled leading to nanofibers by the formation of double helix between the long amylose graft chains in the intermolecular NaCMC chains of the products. The lengths of the fibers were depended on degrees of polymerization of amylose chains. The nanofiber films were constructed by drying the alkaline solutions of the amylose-grafted NaCMC. The lengths of the nanofibers strongly affected their arrangements in the films. The nanofibers were merged further by washing out alkali to produce the robust nanofiber films. PMID:22939353

Kadokawa, Jun-ichi; Arimura, Takuya; Takemoto, Yasutaka; Yamamoto, Kazuya

2012-10-15

244

Grafting of Poly(n-butylacrylate)-b-poly(2-hydroxyethyl methacrylate) on Carbon Fiber and its Effect on Composite Properties  

Microsoft Academic Search

A treatment method based on the grafting of block copolymer on carbon fiber (CF) surface was proposed for obtaining a controlled interface between carbon fibers and epoxy resin. The block copolymer poly(n-butylacrylate)-b-poly(2-hydroxyethyl methacrylate) (PnBA-b-PHEMA) was grafted on the CF by controlled polymerization. Research shows that the grafting block copolymer can improve interfacial adhesion, and the chain structure, lengths and grafting

Jingqiang Hou; Xiaodong Zhou; Xinggui Zhou

2011-01-01

245

Biostability and biocompatibility of a surface-grafted phospholipid monolayer on a solid substrate  

Microsoft Academic Search

We have previously demonstrated phosphorylcholine monolayer chemically grafted onto a methacryloyl-terminated solid substrate by in situ polymerization. The in situ polymerization was carried out at the interface between a pre-assembled acrylated phospholipid monolayer produced by vesicle fusion and a methacryloyl-terminated substrate using a water-soluble initiator, 2,2?-azobis(2-methylpropionamidine) dihydrochloride (AAPD). Herein, we examined the biostability and biocompatibility of a surface-grafted phospholipid monolayer

Kwangmeyung Kim; Chulhee Kim; Youngro Byun

2004-01-01

246

Chain Reaction Polymerization.  

ERIC Educational Resources Information Center

The salient features and importance of chain-reaction polymerization are discussed, including such topics as the thermodynamics of polymerization, free-radical polymerization kinetics, radical polymerization processes, copolymers, and free-radical chain, anionic, cationic, coordination, and ring-opening polymerizations. (JN)

McGrath, James E.

1981-01-01

247

Structure–property relationships of irradiation grafted nano-inorganic particle filled polypropylene composites  

Microsoft Academic Search

An irradiation grafting method was applied for the modification of nanoparticles so that the latter can be added to polymeric materials for improving their mechanical performance, using existing compounding techniques. The following items are discussed in particular, in this paper: (a) chemical interaction between the grafting monomers and the nanoparticles during irradiation; (b) properties including modulus, yield strength, impact strength

Min Zhi Rong; Ming Qiu Zhang; Yong Xiang Zheng; Han Min Zeng; R Walter; K Friedrich

2001-01-01

248

Electrostrictive Graft Elastomers  

NASA Technical Reports Server (NTRS)

An electrostrictive graft elastomer has a backbone molecule which is a non-crystallizable, flexible macromolecular chain and a grafted polymer forming polar graft moieties with backbone molecules. The polar graft moieties have been rotated by an applied electric field, e.g., into substantial polar alignment. The rotation is sustained until the electric field is removed. In another embodiment, a process for producing strain in an elastomer includes: (a) providing a graft elastomer having a backbone molecule which is a non-crystallizable, flexible macromolecular chain and a grafted polymer forming polar graft moieties with backbone molecules; and (b) applying an electric field to the graft elastomer to rotate the polar graft moieties, e.g., into substantial polar alignment.

Su, Ji (Inventor); Harrison, Joycelyn S. (Inventor); St.Clair, Terry L. (Inventor)

2003-01-01

249

Two Photon Polymerization of Ormosils  

NASA Astrophysics Data System (ADS)

In this work, 3D structures of hybrid polymers—ORMOSILS (organically modified silicates) were produced via Two Photon Polymerization (2PP) of hybrid methacrylates based on silane derivates. Synthetic routes have been used to obtain series of hybrid monomers, their structure and purity being checked by NMR Spectroscopy and Fourier Transform Infrared Spectroscopy. Two photon polymerization method (a relatively new technology which allows fast micro and nano processing of three-dimensional structures with application in medical devices, tissue scaffolds, photonic crystals etc) was used for monomers processing. As laser a Ti: Sapphire laser was used, with 200 fs pulse duration and 2 kHz repetition rate, emitting at 775 nm. A parametric study on the influence of the processing parameters (laser fluence, laser scanning velocity, photo initiator) on the written structures was carried out. The as prepared polymeric scaffolds were tested in mesenchymal stem cells and fibroblasts cell cultures, with the aim of further obtaining bone and dermal grafts. Cells morphology, proliferation, adhesion and alignment were analyzed for different experimental conditions.

Matei, A.; Zamfirescu, M.; Jipa, F.; Luculescu, C.; Dinescu, M.; Buruiana, E. C.; Buruiana, T.; Sima, L. E.; Petrescu, S. M.

2010-10-01

250

Structure, thermodynamics, mechanical properties and glassy dynamics in anisotropic polymeric materials  

Microsoft Academic Search

Anisotropic polymeric materials are ubiquitous. They can form via self assembly, external mechanical deformation or by geometric confinement. Important examples of anisotropic polymeric materials include liquid crystalline polymers and elastomers, amorphous rubber networks, confined films and grafted polymer brushes. A common feature of these materials is the anisotropic conformation of the constituent polymer chains which leads to significant modification of

Folusho Taiwo Oyerokun

2005-01-01

251

Preparation of functionalized polystyrene latexes by radiation-induced miniemulsion polymerization using a Y-type polymerizable surfactant as sole stabilizers  

NASA Astrophysics Data System (ADS)

Functionalized polystyrene latexes were prepared by miniemulsion polymerization using a Y-type polymerizable surfactant bearing a carboxylic acid group as sole stabilizers. Kinetics analysis showed that there was no constant rate stage, which coincided with the kinetics mechanism of the typical miniemulsion polymerization. The latexes obtained were characterized by transmission electron microscopy (TEM), X-ray photoelectron spectroscopy (XPS) and Fourier transform infrared (FTIR) spectroscopy. It was found that the latexes prepared by miniemulsion polymerization initiated by gamma-ray had more narrowly particle size distribution compared with by potassium persulfate. XPS and FTIR results indicated that the carboxyl group was present on the surface of the polymer particles.

Chen, Jun; Zhang, Zhicheng; Zhang, Qianfeng

2009-11-01

252

Synthesis of a novel water-soluble polymeric UV-absorber for cotton  

Microsoft Academic Search

A water-soluble polymeric UV-absorber with polyvinylamine as backbone and benzotriazole type UV absorber as anti-UV functional group was synthesized by grafting brominated (2?-acetoxy-5?-methylphenyl)-2H-benzotriazole onto polyvinylamine. The intermediates and synthesized polymeric UV absorber were characterized by 1H NMR, MS, IR and UV spectroscopy. The finishing properties of the polymeric UV absorber on cotton were investigated to show good UV protection property

Wei Ma; Xue Jiang; Yong Liu; Bing Tao Tang; Shu Fen Zhang

2011-01-01

253

Preparation of functional composite grafted particles PDMAEMA/SiO 2 and preliminarily study on functionality  

NASA Astrophysics Data System (ADS)

Micron-sized silica gel particles were first surface-modified with coupling agent, ?-methacryloylpropyl trimethoxysilane (MPS), and the polymerizable double bonds were introduced onto the surfaces of silica gel particles, forming the modified particles MPS-SiO 2. Subsequently, N,N-dimethylaminoethyl methacrylate (DMAEMA) was graft-polymerized on the surfaces of particles MPS-SiO 2 in the manner of "grafting through", resulting in the grafted particles PDMAEMA/SiO 2. The grafted particles PDMAEMA/SiO 2 were fully characterized with several means. The graft polymerization process of DMAEMA on particles MPS-SiO 2 was studied in detail, and the optimal reaction conditions were determined. Thereafter, the adsorption properties of the grafted particles PDMAEMA/SiO 2 for chromate anion and Cu 2+ ion were preliminarily examined respectively. The experimental results indicate that the PDMAEMA grafting degree on PDMAEMA/SiO 2 particles is limited because an enwinding polymer layer as a kinetic barrier on the surfaces of silica gel particles will be formed during the graft polymerization, and blocks the graft polymerization. In order to enhance PDMAEMA grafting degree, reaction time and temperature, and the used amount of initiator as well as the monomer concentration should be effectively controlled. The preliminary adsorption tests show that the grafted particles PDMAEMA/SiO 2 are multi-functional. They possess very strong adsorption ability for CrO 42- anion by right of strong electrostatic interaction, and have also adsorption action towards heavy metal ion by dint of complexing action.

Gao, Baojiao; Chen, Yinxin; Zhang, Zhenguo

2010-10-01

254

Preparation of poly(ether ether ketone)-based polymer electrolytes for fuel cell membranes using grafting technique  

Microsoft Academic Search

Poly(ether ether ketone) (PEEK)-based polymer electrolyte membranes (PEMs) was successfully prepared by radiation grafting of a styrene monomer into PEEK films and the consequent selective sulfonation of the grafting chains in the film state. Using milder sulfonation, the sulfonation reactions proceeded at the grafted chains in preference to the phenylene rings of PEEK main chains; as a result, the grafted

Shin Hasegawa; Yasuyuki Suzuki; Yasunari Maekawa

2008-01-01

255

Skin graft - series (image)  

MedlinePLUS

... entire body, and acts as a protective barrier. Skin grafts may be recommended for: extensive wounds burns specific surgeries that may require skin grafts for healing to occur. The most common sites ...

256

Polymerization of perfluorobutadiene at near-ambient conditions  

NASA Technical Reports Server (NTRS)

Peroxide catalyst under mild conditions initiates homopolymerization of perfluoro butadiene to new linear perfluoro polyenes and vulcanizable fluoro elastomers. Resulting polyperfluoro butadiene serves as hard elastomer for good chemical resistance, as intermediate in graft polymerizations, and as crosslink for high molecular weight materials.

Toy, M. S.

1971-01-01

257

Bone grafts in dentistry  

PubMed Central

Bone grafts are used as a filler and scaffold to facilitate bone formation and promote wound healing. These grafts are bioresorbable and have no antigen-antibody reaction. These bone grafts act as a mineral reservoir which induces new bone formation. PMID:23946565

Kumar, Prasanna; Vinitha, Belliappa; Fathima, Ghousia

2013-01-01

258

A facile metal-free "grafting-from" route from acrylamide-based substrate toward complex macromolecular combs.  

PubMed

High-molecular-weight poly(N,N-dimethylacrylamide-co-acrylamide) was used as a model functional substrate to investigate phosphazene base (t-BuP4)-promoted metal-free anionic graft polymerization utilizing primary amide moieties as initiating sites. The (co)polymerization of epoxides was proven to be effective, leading to macromolecular combs with side chains being single- or double-graft homopolymer, block copolymer and statistical copolymer. PMID:23824060

Zhao, Junpeng; Alamri, Haleema; Hadjichristidis, Nikos

2013-08-14

259

Loading amplification of radiation grafted polymers (crowns and lanterns) and their application in the solid-phase synthesis of hydantoin libraries  

Microsoft Academic Search

Solid-phase dendrimer chemistry using a symmetrical 1?3C-branched isocyanate monomer was used to prepareradiation-grafted polymers with enhanced loading. Afterevaluation of the physical and chemical properties of thesenew high-loading supports, they were tested in the multipleparallel synthesis of hydantoins.

Sylvain Lebreton; Nicholas Newcombe; Mark Bradley

2003-01-01

260

Polymeric Materials for Tissue Engineering of Arterial Substitutes  

PubMed Central

Cardiovascular disease is the leading cause of mortality in the United States. The limited availability of healthy autologous vessels for bypass grafting procedures has led to the fabrication of prosthetic vascular conduits. Synthetic polymeric materials, while providing the appropriate mechanical strength, lack the compliance and biocompatibility that bioresorbable and naturally occurring protein polymers offer. Vascular tissue engineering approaches have emerged in order to meet the challenges of designing a vascular graft with long-term patency. In vitro culture techniques that have been explored with vascular cell seeding of polymeric scaffolds and the use of bioactive polymers for in situ arterial regeneration have yielded promising results. This review describes the development of polymeric materials in various tissue engineering strategies for the improvement in the mechanical and biological performance of an arterial substitute. PMID:19426609

Ravi, Swathi; Qu, Zheng; Chaikof, Elliot L.

2009-01-01

261

Grafting of 2 (2-hydroxy-5-vinylphenyl) 2H-benzotriazole onto polymers with aliphatic groups. Synthesis and polymerization of 2 (2-hydroxy-5-isopropenylphenyl) 2H-benzotriazole and a new synthesis of 2 (2-hydroxy-5-vinylphenyl) 2H-benzotriazole  

NASA Technical Reports Server (NTRS)

Successful grafting of 2(2-hydroxy-5-vinylphenyl)2H-benzotriazole onto saturated aliphatic C-H groups of polymers has been accomplished. When the grafting reaction was carried out in chlorobenzene at 150 C = 160 C with di-tertiarybutylperoxide as the grafting initiator, grafts as high as 20 percent - 30 percent at a grafting efficiency of 50 percent and 80 percent have readily been obtained. The grafting reaction was carried out in tubes sealed under high vacuum since trace amounts of oxygen cause complete inhibition of the grafting reaction by the phenolic monomer. On a variety of different polymers including atactic polypropylene, ethylene/vinyl acetate copolymer, poly(methyl methacrylate), poly(butyl acrylate), and polycarbonate were used.

Pradellok, W.; Nir, Z.; Vogl, O.

1981-01-01

262

Surface-grafted polypeptides on flat substrates  

NASA Astrophysics Data System (ADS)

In this work, we improved the vapor deposition-polymerization (VDP) technique by re-designing a new vacuum chamber, and adding two heating plates to control the temperatures of the substrate and monomer evaporation. By optimizing the reaction parameters such as monomer amount, substrate temperature and reaction time, various polypeptides with sufficiently high molecular weight have been successfully grafted onto the solid substrates. The combination of VPD with photolithography has fabricated micro-patterned polypeptides, with geometry patternable in both lateral and vertical directions. Next, the conformations of the surface-grafted polypeptides were systematically examined. New ways have been found to switch their conformations between alpha-helix and beta-sheet, or between right-handed helix and left-handed helix. Two important ionic polypeptides, poly(L-glutamic acid) (PLGA) and poly(L-lysine) (PLL) were the focuses of this work. The conformational transitions of surface-grafted PLGA and PLL were successfully induced by pH, surfactants and ions. In addition, a surface-grafted PLGA-block-PLL copolypeptide was studied. Their unexpected pH-responsiveness was explained by the beta-sheet formation between the PLGA and PLL blocks. The orientation of the surface-grafted alpha-helical poly(gamma-benzyl L-glutamate) (PBLG) was greatly improved by a novel "solvent quenching" method, which involves treating the film sequentially with a good solvent and a poor solvent. The average tilt angle of the PBLG rods changed from 49° to 3° by applying this "quenching". Finally, a surface-grafted PLL film was used as the template to mimic the biosilicification. Silica was spontaneously synthesized from tetraethoxysilane inside the PLL film at room temperature and at neutral pH.

Wang, Yuli

263

Kinetics of swelling assisted grafting of 4-vinyl pyridine onto poly(ethylene terephthalate) fibers using a benzoyl peroxide initiator  

Microsoft Academic Search

Summary Poly(ethylene terephthalate) (PET) fibers were grafted with 4-vinyl pyridine (4-VP) using benzoyl peroxide (Bz 2O 2) as initiator. Fibers were swelled in dichloroethane (DCE) for 2 h at 90 °C to promote the incorporation and the subsequent polymerization of 4-VP onto PET fibers. Variations of graft yield with time, temperature, initiator and monomer concentrations were investigated. Percent grafting was

Metin Arslan; Mustafa Yigitoglu; Oya Sanli; Halil Ibrahim Ünal

2003-01-01

264

Polymeric materials in Space  

NASA Astrophysics Data System (ADS)

Paper of short review type. It is the continuation of and addition to previous review papers "V. E. Skurat. Polymers in Space. In: Encyclopedia of aerospace engineering, vol. 4, Wiley and sons, 2010; Ibid., 2012 (on line)". Following topics are considered: (1) Destruction of polymers by solar radiation with various wavelengths in different spectral regions (visible-UV, vacuum UV (VUV), deep UV, soft and hard X-rays) are discussed. In difference with common polymer photochemistry induced by UV radiation, directions of various routs of polymer phototransformations and their relative yields are greatly dependent on wavelength of light (photon energy) during illuminations in VUV, deep UV and X-ray regions. During last twenty years, intensive spacecraft investigations of solar spectrum show great periodic and spontaneous variations of radiation intensities in short-wavelengths regions - up to one - two decimal orders of magnitude for X-rays. As a result, during solar flares the absorbed dose on the polymer surfaces from X-rays can be compared with absorbed dose from VUV radiation. (2) Some new approaches to predictions of reaction efficiencies of fast orbital atomic oxygen in their interaction with polymeric materials are considered. (3) Some aspects of photocatalitic destruction of polymers in vacuum conditions by full-spectrum solar radiation are discussed. This process can take place in enamels containing semiconducting particles (TiO2, ZnO) as pigments. (4) Contamination of spacecraft surfaces from intrinsic outer atmosphere play important role not only from the point of view of deterioration of optical and thermophysical properties. Layers of SiO2 contaminations with nanometer thicknesses can greatly diminish mass losses from perfluorinated polymers under VUV irradiation.

Skurat, Vladimir

265

Polymerization of perfluorobutadiene  

NASA Technical Reports Server (NTRS)

Diisopropyl peroxydicarbonate dissolved in liquid perfluorobutadiene is conducted in a sealed vessel at the autogenous pressure of polymerization. Reaction temperature, ratio of catalyst to monomer, and amount of agitation determine degree of polymerization and product yield.

Newman, J.; Toy, M. S.

1970-01-01

266

Light-responsive polymer surfaces via postpolymerization modification of grafted polymer-brush structures.  

PubMed

Light-induced, spatially well-defined, reversible switching of surface properties enables the creation of remote-controlled smart surfaces. We have taken advantage of the unique high-resolution structuring capabilities of extreme ultraviolet (EUV) interference lithography to produce nanostructured photoresponsive polymer brushes. Patterns of poly(glycidyl methacrylate) (PGMA) and poly(methacrylic acid) (PMAA) were grafted from two different 100 ?m thick fluoropolymer substrates by means of a radiation-initiated, grafting-from approach based on free-radical polymerization (FRP). Photochromic properties were introduced via novel one- or two-step postpolymerization modifications with spiropyran (SP) derivatives, which allowed us to control the number of photochromic groups on the polymer brushes. Depending on the degree of functionalization and the local chemical environment, the SP moieties can open upon UV-light exposure to form zwitterionic, deeply colored, and fluorescent merocyanines (MCs) and reclose to the colorless SP configuration via thermal or visible light-induced relaxation. Switching kinetics were studied by means of time-resolved fluorescence microscopy and compared with kinetic measurements of the SP moiety in solution. The results indicated the importance, for the intensity of the switching, of the local chemical environment provided by both the polymer brush and added solvents, and showed the predominant influence on the ring-closing kinetics of polar solvents, which stabilize the MC form. To allow further characterization of the polymer-brush arrangements on a macroscopic scale, similar, but unstructured brush systems were grafted from fluoropolymers after large-area activation using EUV radiation or argon plasma. All steps of the postpolymerization modification were characterized in detail using attenuated total reflection infrared (ATR-IR) spectroscopy. Furthermore, a light-induced reversible static-contact-angle switch with a range of up to 15° for PGMA-SP brushes and up to 30° for PMA-SP brushes was demonstrated upon alternating UV- and visible-light irradiation. PMID:25419582

Dübner, Matthias; Spencer, Nicholas D; Padeste, Celestino

2014-12-16

267

Accelerated cell-sheet recovery from a surface successively grafted with polyacrylamide and poly(N-isopropylacrylamide).  

PubMed

A double polymeric nanolayer consisting of poly(N-isopropylacrylamide) (PIPAAm) and hydrophilic polyacrylamide (PAAm) was deposited on tissue culture polystyrene (TCPS) surfaces using electron beam irradiation to form a new temperature-responsive cell culture surface in which the basal hydrophilic PAAm component in the double polymeric layer promotes the hydration of the upper PIPAAm layer and induces rapid cell detachment compared to a conventional temperature-responsive cell culture surface, PIPAAm-grafted TCPS (PIPAAm-TCPS). Take-off angle-dependent X-ray photoelectron spectroscopy spectral analysis demonstrated that the grafted PIPAAm and PAAm components were located in the upper and basal regions of the double polymeric layer, respectively, suggesting that the double polymeric layer forms an inter-penetrating-network-like structure with PAAm at the basal portion of the PIPAAm grafted chains. The wettability of the temperature-responsive cell culture surfaces with the double polymeric layer tended to be more hydrophilic, with an increase in the basal PAAm graft density at a constant PIPAAm graft density. However, when the graft densities of the upper PIPAAm and basal PAAm were optimized, the resulting temperature-responsive cell culture surface with the double polymeric layer exhibited rapid cell detachment while maintaining cell adhesive character comparable to that of PIPAAm-TCPS. The cell adhesive character was altered from cell-adhesive to cell-repellent with increasing PAAm or PIPAAm graft density. The cell adhesive character of the temperature-responsive cell culture surfaces was relatively consistent with their contact angles. These results strongly suggest that the basal PAAm surface properties affect the degree of hydration and dehydration of the subsequently grafted PIPAAm. In addition, the roles of the hydrophilic component in accelerating cell detachment are further discussed in terms of the mobility of the grafted PIPAAm chains. Applications of this insight might be useful for designing temperature-responsive cell culture surfaces for achieving efficient cell culture and quick target cell detachment. PMID:24681372

Akiyama, Yoshikatsu; Kikuchi, Akihiko; Yamato, Masayuki; Okano, Teruo

2014-08-01

268

Study on grafting of different types of acrylic monomers onto natural rubber by ?-rays  

NASA Astrophysics Data System (ADS)

A comparative study of various acrylic monomers for grafting onto natural rubber was done. The stability of natural rubber latex (NRL) against coagulum with monomer, mechanical properties of grafted rubbers and percent of grafting were investigated. The NRL with monomers, methylacrylate (MA), ethylacrylate (EA) and n-butylacrylate ( n-BA), is unstable but it is stable with methyl methacrylate (MMA), n-butyl methacrylate (BMA) and cyclohexyl methacrylate (CHMA). The mechanical properties and degree of grafting attained a maximum at a total radiation dose of 4 kGy. The values of tensile properties of MMA and CHMA grafted rubbers are almost similar, and higher than those of BMA grafted rubbers. On the other hand, the degree of grafting for CHMA is higher than those of MMA and BMA grafted rubbers. The infrared (IR) spectra of monomer grafted natural rubber were also studied.

Dafader, N. C.; Haque, M. E.; Akhtar, F.; Ahmad, M. U.

2006-01-01

269

Anticancer Polymeric Nanomedicines  

Microsoft Academic Search

Polymers play important roles in the design of delivery nanocarriers for cancer therapies. Polymeric nanocarriers with anticancer drugs conjugated or encapsulated, also known as polymeric nanomedicines, form a variety of different architectures including polymer?drug conjugates, micelles, nanospheres, nanogels, vesicles, and dendrimers. This review focuses on the current state of the preclinical and clinical investigations of polymer?drug conjugates and polymeric micelles.

Rong Tong; Jianjun Cheng

2007-01-01

270

Polymerization Reactor Engineering.  

ERIC Educational Resources Information Center

Describes a polymerization reactor engineering course offered at Michigan Technological University which focuses on the design and operation of industrial polymerization reactors to achieve a desired degree of polymerization and molecular weight distribution. Provides a list of the course topics and assigned readings. (TW)

Skaates, J. Michael

1987-01-01

271

Anastomotic stenting in a porcine aortoiliac graft model.  

PubMed

The purpose of the study was to evaluate the feasibility of anastomotic stent application in a porcine aortoiliac graft model. In a total of 10 pigs, a polytetrafluoroethylene aortobi-iliac graft was implanted through a midline abdominal incision. The lower edge of the iliac vessel was graft-inverted about 1 mm to produce irregularities at the downstream anastomosis. After transverse graft incision, six stainless-steel stents, six poly-L-lactic acid (PLLA) stents and four PLLA stents with 10% polycaprolactone (PCL) were implanted at the iliac anastomotic site using a 6 mm balloon dilatation catheter. Four anastomotic sites were left untreated. After two weeks, the patency of graft limbs was evaluated by contrast-enhanced computed tomography (CT). Both metal and polymeric stent designs provided adequate flexibility to manoeuvre across the anastomotic site for expansion in the chosen position. After deployment, the stent-arterial wall contact was complete on a macroscopic view. On CT scan, all metal and PLLA-stented graft limbs were free of stenosis, whereas all PLLA/PCL stents were occluded. The non-stented graft limbs showed a stenosis of 50-70%. In summary, this model is feasible to assess preclinically the deployment and patency rate of an anastomotic stent and to test future stent developments. PMID:17234052

Bünger, C M; Grabow, N; Hauenstein, K; Ketner, L; Kröger, Chr; Sternberg, K; Kramer, S; Lootz, D; Schmitz, K-H; Kreutzer, H J; Klar, E; Schareck, W

2007-01-01

272

Hydroxyalkylation and polyether polyol grafting of graphene tailored for graphene/polyurethane nanocomposites.  

PubMed

Graphene functionalization by hydroxyalkylation and grafting with polyether polyols enables polyurethane (PU) nanocomposites formation by in situ polymerization with isocyanates combined with effective covalent interfacial coupling. Functionalized graphene (FG) hydroxylation is achieved either by alkylation, transesterification, or grafting of thermally reduced graphite oxide. In the presence of K2 CO3 as catalyst the reaction of FG-OH with ethylene carbonate at 180 °C affords hydroxyethylated FG, whereas transesterification with castor oil produces riconoleiate-modified FG polyols. In the "grafting-from" process, FG-alkoholate macro initiators initiate the graft polymerization of propylene oxide to produce hybrid FG polyols containing 38 and 59 wt% oligopropylene oxide. In the "grafting-to" process 3-ethyl-3-hydroxymethyl-oxetane is cationically polymerized onto FG-OH, producing novel hyperbranched FG-based polyether polyols. Whereas hydroxylation and grafting of FG greatly improve FG dispersion in organic solvents, polyols and even PU, as confirmed by transmission electron microscopy, matrix reinforcement of FG/PU is impaired by increasing alkyl chain length and polyol graft copolymer content. PMID:23836705

Appel, Anna-Katharina; Thomann, Ralf; Mülhaupt, Rolf

2013-08-01

273

Gum Graft Surgery  

MedlinePLUS

... Comprehensive Periodontal Evaluation Periodontal Treatments and Procedures Non-Surgical Periodontal Treatments Gum Graft Surgery Laser Treatment for Gum Disease Regenerative Procedures Dental Crown ...

274

Staple viscose rayon modified with graft polystyrene  

Microsoft Academic Search

the necessary processability in the weaving and knitting sectors. The staff of the laboratories of the Moscow Textile Institute have produced several modified viscose rayon staple fibres by grafting with various monomers. One of these is based on a co-polymer of cellulose with polystyrene. The fibre is highly hydrophobic and stable to mineral acids and UV and y radiation \\/2\\/

M. P. Berezeva; E. N. Chernov; B. P. Morin; Z. A. Rogovin

1973-01-01

275

A Versatile Star PEG Grafting Method for the Generation of Nonfouling and Nonthrombogenic Surfaces  

PubMed Central

Polyethylene glycol (PEG) grafting has a great potential to create nonfouling and nonthrombogenic surfaces, but present techniques lack versatility and stability. The present work aimed to develop a versatile PEG grafting method applicable to most biomaterial surfaces, by taking advantage of novel primary amine-rich plasma-polymerized coatings. Star-shaped PEG covalent binding was studied using static contact angle, X-ray photoelectron spectroscopy (XPS), and quartz crystal microbalance with dissipation monitoring (QCM-D). Fluorescence and QCM-D both confirmed strong reduction of protein adsorption when compared to plasma-polymerized coatings and pristine poly(ethyleneterephthalate) (PET). Moreover, almost no platelet adhesion was observed after 15?min perfusion in whole blood. Altogether, our results suggest that primary amine-rich plasma-polymerized coatings offer a promising stable and versatile method for PEG grafting in order to create nonfouling and nonthrombogenic surfaces and micropatterns. PMID:23509823

Thalla, Pradeep Kumar; Contreras-García, Angel; Fadlallah, Hicham; Barrette, Jérémie; De Crescenzo, Gregory; Merhi, Yahye; Lerouge, Sophie

2013-01-01

276

Cranial nasal bone grafts  

Microsoft Academic Search

Reconstitution of the nasal scaffolding with maintainence of soft tissue proportions either following severe facial trauma or as a sequela to aesthetic rhinoplasty misadventures frequently is best achieved using the stability afforded by bone grafts. Split cranial bone grafts offer many advantages and may be the donor site of choice, and may even allow such surgery to be performed on

Geoffrey G. Hallock

1989-01-01

277

Skin graft (image)  

MedlinePLUS

A skin graft is a surgical procedure in which a piece of skin is transplanted from one area to another. ... a great loss of tissue, a full thickness graft, a flap of skin with underlying muscle and blood vessels, may be ...

278

Alveolar bone grafting.  

PubMed

In the 1970s, Boyne and Sands published reports on a new technique for alveolar bone grafting. They recommended that only cancellous bone be used and that the procedure be undertaken in the mixed dentition prior to canine eruption. Alveolar bone grafting prior to canine eruption soon became a routine part of the protocol for 90% of European and North American cleft teams. Several uncertainties remain however, such as the specifics of the surgical and orthodontic procedures, type of bone and donor site, and the best way to manage the space in the dental arch. Probably the commonest timing of the bone graft falls between 8 and 11 years, however there has been a trend in some centres to graft earlier in the hope of better outcome for the unerupted incisors. The influence on maxillary growth of earlier grafting has not been ascertained. A wide range of donor sites has been use but iliac crest remains the most popular. Many teams perform orthodontics prior to grafting to correct severe segment displacement or align incisors to improve surgical access. Following grafting, absence of the lateral incisor may be managed with orthodontic space closure, placement of an implant or bridgework. The introduction of alveolar bone grafting probably represents one of the most significant clinical innovations in cleft care. Hopefully, advances in tissue engineering will replace the need for transplantation of autogenous bone, or will provide an in-situ biological solution to the generation of a continuous bone fill across the alveolar cleft. PMID:22759676

Semb, Gunvor

2012-01-01

279

Free radical grafting kinetics of acrylamide onto a blend of starch/chitosan/alginate.  

PubMed

Grafting of monomer onto polymer backbone is one of the effective and accessible methods for the chemical modification of polysaccharides. Grafting of acrylamide (AAm) onto polysaccharides blend (PsB) composed of starch, chitosan and alginate has been carried out using potassium persulfate (KPS) as an initiator. The kinetics of the grafting polymerization also has been studied. The grafting parameters have been evaluated by changing the initial concentrations of AAm from 8 to 16 g, PsB from 6 to 14 g and KPS from 0.2 to 1 g. Evidence of grafting has been obtained from FTIR, XRD and TGA. The kinetics of the grafting polymerization also has been studied. The grafting rate equation of the produced hydrogel (PsB-g-AAm) hydrogel has been expressed by: Rg=k[AAm] [PsB](0.5) [KPS](0.5). The grafting rate is a first order dependence to [AAm] initial concentration and square root to [PsB] and [KPS] initial concentrations in the used concentrations range. PMID:23987368

Sorour, Mohamed; El-Sayed, Marwa; El Moneem, Nabil Abd; Talaat, Hala; Shaalan, Hayam; El Marsafy, Sahar

2013-10-15

280

Controlled atom transfer radical polymerization of MMA onto the surface of high-density functionalized graphene oxide  

PubMed Central

We report on the grafting of poly(methyl methacrylate) (PMMA) onto the surface of high-density functionalized graphene oxides (GO) through controlled radical polymerization (CRP). To increase the density of surface grafting, GO was first diazotized (DGO), followed by esterification with 2-bromoisobutyryl bromide, which resulted in an atom transfer radical polymerization (ATRP) initiator-functionalized DGO-Br. The functionalized DGO-Br was characterized by X-ray photoelectron spectroscopy (XPS), Raman, and XRD patterns. PMMA chains were then grafted onto the DGO-Br surface through a ‘grafting from’ technique using ATRP. Gel permeation chromatography (GPC) results revealed that polymerization of methyl methacrylate (MMA) follows CRP. Thermal studies show that the resulting graphene-PMMA nanocomposites have higher thermal stability and glass transition temperatures (Tg) than those of pristine PMMA. PMID:25114639

2014-01-01

281

Controlled atom transfer radical polymerization of MMA onto the surface of high-density functionalized graphene oxide  

NASA Astrophysics Data System (ADS)

We report on the grafting of poly(methyl methacrylate) (PMMA) onto the surface of high-density functionalized graphene oxides (GO) through controlled radical polymerization (CRP). To increase the density of surface grafting, GO was first diazotized (DGO), followed by esterification with 2-bromoisobutyryl bromide, which resulted in an atom transfer radical polymerization (ATRP) initiator-functionalized DGO-Br. The functionalized DGO-Br was characterized by X-ray photoelectron spectroscopy (XPS), Raman, and XRD patterns. PMMA chains were then grafted onto the DGO-Br surface through a `grafting from' technique using ATRP. Gel permeation chromatography (GPC) results revealed that polymerization of methyl methacrylate (MMA) follows CRP. Thermal studies show that the resulting graphene-PMMA nanocomposites have higher thermal stability and glass transition temperatures ( T g) than those of pristine PMMA.

Kumar, Mukesh; Chung, Jin Suk; Hur, Seung Hyun

2014-07-01

282

Antifouling nanofiltration membranes for membrane bioreactors from self-assembling graft copolymers  

Microsoft Academic Search

Ultrafiltration (UF) membranes, often employed in membrane bioreactors (MBRs), exhibit high susceptibility to fouling by extracellular polymeric substances (EPS). As potential alternatives, commercial polyvinylidene fluoride (PVDF) UF membranes were coated with the amphiphilic graft copolymer poly(vinylidene fluoride)-graft-poly(oxyethylene) methacrylate, PVDF-g-POEM, to create thin film composite (TFC) nanofiltration membranes. Pure water permeabilities up to 56L\\/m2hMPa were obtained at pressures of 0.21MPa (30psi).

Ayse Asatekin; Adrienne Menniti; Seoktae Kang; Menachem Elimelech; Eberhard Morgenroth; Anne M. Mayes

2006-01-01

283

Thermally sprayable grafted LDPE\\/nanoclay composite coating for corrosion protection  

Microsoft Academic Search

Application of thermally sprayable polymeric coating is one of the methods for protection of mild steel against corrosion. In the present study, grafting of low density polyethylene (LDPE) was carried out with maleic acid at different concentrations (3, 5, 8 and 10%, w\\/v) using ?-irradiation technique. LDPE, ?-irradiated LDPE and grafted LDPE (LDPE-g-MAc) were characterized by chemical method, Fourier transform

Rashmi David; S. P. Tambe; S. K. Singh; V. S. Raja; Dhirendra Kumar

2011-01-01

284

ATRP of Amphiphilic Graft Copolymers Based on PVDF and Their Use as Membrane Additives  

Microsoft Academic Search

The direct preparation of amphiphilic graft copolymers from commercial poly(vinylidene fluoride) (PVDF) using atom transfer radical polymerization (ATRP) is demonstrated. Here, direct initiation of the secondary fluorinated site of PVDF facilitates grafting of the hydrophilic comonomer. Amphiphilic comb copolymer derivatives of PVDF having poly(methacrylic acid) side chains (PVDF-g- PMAA) and poly(oxyethylene methacrylate) side chains (PVDF-g-POEM) are prepared using this method.

J. F. Hester; P. Banerjee; Y.-Y. Won; A. Akthakul; M. H. Acar; A. M. Mayes

2002-01-01

285

Chemically induced graft copolymerization of 2-hydroxyethyl methacrylate onto polyurethane surface for improving blood compatibility  

NASA Astrophysics Data System (ADS)

To improve hydrophilicity and blood compatibility properties of polyurethane (PU) film, we chemically induced graft copolymerization of 2-hydroxyethyl methacrylate (HEMA) onto the surface of polyurethane film using benzoyl peroxide as an initiator. The effects of grafting temperature, grafting time, monomer and initiator concentrations on the grafting yields were studied. The maximum grafting yield value was obtained 0.0275 g/cm2 for HEMA. Characterization of the films was carried out by attenuated total reflection Fourier transform infrared spectroscopy (ATR-FTIR), water contact angle measurements. ATR-FTIR data showed that HEMA was successfully grafted onto the PU films surface. Water contact angle measurement demonstrated the grafted films possessed a relatively hydrophilic surface. The blood compatibility of the grafted films was preliminarily evaluated by a platelet-rich plasma adhesion test and hemolysis test. The results of platelet adhesion experiment showed that polyurethane grafted polymerization with monomer of 2-hydroxyethyl methacrylate had good blood compatibility featured by the low platelet adhesion. Hemolysis rate of the PU-g-PHEMA films was dramatically decreased than the ungrafted PU films. This kind of new biomaterials grafted with HEMA monomers might have a potential usage for biomedical applications.

He, Chunli; Wang, Miao; Cai, Xianmei; Huang, Xiaobo; Li, Li; Zhu, Haomiao; Shen, Jian; Yuan, Jiang

2011-11-01

286

Polypeptoid Brushes by Surface-Initiated Polymerization of N-Substituted Glycine N-Carboxyanhydrides  

PubMed Central

Polypeptoid brushes were synthesized by surface-initiated polymerization of N-substituted glycine N-carboxyanhydrides (NNCAs) on self assembled amine monolayers. Using the presented grafting from approach, polypeptoid brush thicknesses of approx. 40 nm could be obtained as compared previously reported brush thicknesses of 4 nm. Moreover, hydrophilic, hydrophobic and amphiphilic polymer brushes were realized which are expected to have valuable applic-tions as non-fouling surfaces and as model or references systems for surface grafted polypeptides. PMID:23663172

Schneider, Maximilian; Fetsch, Corinna; Amin, Ihsan; Jordan, Rainer; Luxenhofer, Robert

2013-01-01

287

Silicon tetrachloride plasma induced grafting for starch-based composites  

Microsoft Academic Search

Non-modified virgin starch is seldom used directly in industrial applications. Instead, it is often physically and\\/or chemically modified to achieve certain enhanced properties. For many of the non-food applications, these modifications involve changing its hydrophilicity to create hydrophobic starch. In this study, the hydrophobic starch was produced through silicon tetrachloride (SiCl4) plasma induced graft polymerization, so that it could be

Yonghui C. Ma

2002-01-01

288

Radiation-grafted fluoropolymers soaked with imidazolium-based ionic liquids for high-performance ionic polymer-metal composite actuators.  

PubMed

On purpose to develop a polymer actuator with high stability in air-operation as well as large bending displacement, a series of ionic polymer-metal composites (IPMC) was constructed with poly(styrene sulfonate)-grafted fluoropolymers as ionomeric matrix and immidazolium-based ionic liquids (IL) as inner solvent. The prepared IPMC actuators exhibited greatly enhanced bending displacement compared to Nafion-based actuators. The actuators were stable in air-operation, maintaining initial displacement for up to 10(4) cycles or 24?h. Investigating the material parameters and morphology of the IPMCs, high ion exchange capacity of the ionomers resulted in high ion conductivity and robust electrode of IPMC, which synergistically contributed to the high bending performance. PMID:21567610

Lee, Jang Yeol; Wang, Hyuck Sik; Yoon, Bye Ri; Han, Man Jae; Jho, Jae Young

2010-11-01

289

Preparation and characterization of saponified delignified cellulose polyacrylonitrile-graft copolymer  

Microsoft Academic Search

Acrylonitrile was graft polymerized onto delignified cellulose using ceric ammonium nitrate as initiator. Polymerization typically yield cellulose-g-polyacrylonitrile containing 45.05g acrylonitrile per 100g sample. The resulting copolymer was saponified with (0.75M) sodium hydroxide. The treatment was carried out at 100°C for different time duration. The extent of saponification was assessed by estimating carboxyl content, nitrogen content, acrylonitrile and acrylic acid before

S. Farag; Eljazi I. Al-Afaleq

2002-01-01

290

Synthesis and Characterization of Photochromic Copolymer Grafting Azoaromatic Chromospheres on Pullulan  

Microsoft Academic Search

Preparation of photochromic copolymer grafting 4-(4-nitro phenylazo)-1-naphthol units on a pullulan molecular surface has been accomplished. Surface modification was carried out in aqueous solution by an inverse emulsion polymerization method. Polymerization products were characterized by IR, SEM, XRD and TG-DTA. UV-vis spectroscopy has been used to monitor the photoisomerization of azobenzene moieties on a pullulan molecular surface. The results indicated

Xinghai Yu; Zhengsheng Fu; Honggang An; Dongqing Wu; Yuqi Han; Hai Song

2010-01-01

291

Insitu grafting silica nanoparticles reinforced nanocomposite hydrogels  

NASA Astrophysics Data System (ADS)

Highly flexible nanocomposite hydrogels were prepared by using silica nanoparticles (SNPs) as fillers and multi-functional cross-links to graft hydrophilic poly(acrylic acid) (PAA) by free radical polymerization from an aqueous solution. The SNPs were collected by neighboring polymer chains and dispersed uniformly within a PAA matrix. The mechanical properties of the nanocomposite hydrogels were tailored by the concentration of SNPs according to the percolation model. It was proposed that covalent bonds of adsorbed chains on the filler surface resulted in the formation of a shell of an immobilized glassy layer and trapped entanglements, where the glassy polymer layer greatly enhanced the elastic modulus and the release of trapped entanglements at deformation contributed to the viscoelastic properties.Highly flexible nanocomposite hydrogels were prepared by using silica nanoparticles (SNPs) as fillers and multi-functional cross-links to graft hydrophilic poly(acrylic acid) (PAA) by free radical polymerization from an aqueous solution. The SNPs were collected by neighboring polymer chains and dispersed uniformly within a PAA matrix. The mechanical properties of the nanocomposite hydrogels were tailored by the concentration of SNPs according to the percolation model. It was proposed that covalent bonds of adsorbed chains on the filler surface resulted in the formation of a shell of an immobilized glassy layer and trapped entanglements, where the glassy polymer layer greatly enhanced the elastic modulus and the release of trapped entanglements at deformation contributed to the viscoelastic properties. Electronic supplementary information (ESI) available: FTIR spectra of SNP after silane treatment, dynamic oscillatory shear measurements as a function of frequency, constrained polymer chain analysis by a change in the peak height in loss factor spectra, molecular weight of grafted chains at different stages of gelation, prediction of the SNP reinforcing mechanism in the frame of the percolation model, cyclic tensile loading-loading behaviors of SNP gels, and the tearing test. See DOI: 10.1039/c3nr04252a

Yang, Jun; Han, Chun-Rui; Duan, Jiu-Fang; Xu, Feng; Sun, Run-Cang

2013-10-01

292

Calcific stenotic jump graft.  

PubMed Central

A young lady with post-subclavian coarctation and cranial hypertension is discussed. She had a jump graft from left subclavian artery to descending aorta, and presented 18 years later with hypertension, calcification of the graft with a gradient of 40 mmHg across it. In the meantime, she also developed moderate aortic regurgitation on a bicuspid aortic valve. Management strategies including trans-catheter options are discussed. We present our reservations on trans-catheter options in an occluded dacron graft. PMID:16749963

Padmakumar, R.; Krishnamoorthy, K. M.; Tharakan, J. A.

2004-01-01

293

Grafted Hydrophilic Polymers As Optical Sensor Substrates  

NASA Astrophysics Data System (ADS)

A prototype fiber optic oxygen sensor was fabricated by grafting poly(2-hydroxyethylmethacrylate) (PHEMA), containing the oxygen quenchable fluorescent dye, 9,10-diphenylanthracene (9,10-D), to a glass fiber. The PHEMA-glass fiber graft was optimized to maximize stability in hydrolytic environments. The fluorescence of the dye was quenched 20% when the sensor went from an oxygen-free to an oxygen-saturated environment. Transient response times of the sensor were reduced when the PHEMA graft thickness was reduced. Modeling of the transient data gave a diffusion coefficient of oxygen in PHEMA of 2.15 x 10-6 cm2/sec. Glucose oxidase (GOO) was incorporated into PHEMA for the ultimate purpose of converting the fiber optic oxygen sensor into a glucose sensor. Immobilization of glucose oxidase was accomplished through a physical entrapment in the PHEMA matrix. Immobilization parameters such as thickness of the polymer layer, enzyme loading, and polymerization conditions were adjusted to give adequate sensitivity in the desired range of glucose concentrations. Immobilized GOx activity was measured over a wide range of enzyme loadings and glucose concentrations. The feasibility of using PHEMA containing 9,10-D and GOx as a material sensitive to physiological levels of glucose was demonstrated.

Shah, Rajiv; Margerum, Suzanne C.; Gold, Michael

1988-06-01

294

Aryl Diazonium Salts for Carbon Fiber Surface-Initiated Atom Transfer Radical Polymerization  

Microsoft Academic Search

N2-C6H4-CH(CH3)-Br diazonium salt was electrochemically reduced in order to graft phenylethyl bromide groups to carbon fibers. The pretreated fibers (CF-Br) served as macroinitiators of atom transfer radical polymerization (ATRP) of vinylic monomers. This procedure combining a diazonium salt and ATRP permitted the polymerization of butyl, glycidyl and hydroxyethyl methacrylates at the surface of carbon fibers (CF) resulting in CF-PBMA, CF-PGMA,

Tarik Matrab; Minh Ngoc Nguyen; Samia Mahouche; Philippe Lang; Chantal Badre; Mireille Turmine; Grégory Girard; Jinbo Bai; Mohamed M. Chehimi

2008-01-01

295

Making Polymeric Microspheres  

NASA Technical Reports Server (NTRS)

Combination of advanced techniques yields uniform particles for biomedical applications. Process combines ink-jet and irradiation/freeze-polymerization techniques to make polymeric microspheres of uniform size in diameters from 100 to 400 micrometer. Microspheres used in chromatography, cell sorting, cell labeling, and manufacture of pharmaceutical materials.

Rhim, Won-Kyu; Hyson, Michael T.; Chung, Sang-Kun; Colvin, Michael S.; Chang, Manchium

1989-01-01

296

Step-Growth Polymerization.  

ERIC Educational Resources Information Center

Following a comparison of chain-growth and step-growth polymerization, focuses on the latter process by describing requirements for high molecular weight, step-growth polymerization kinetics, synthesis and molecular weight distribution of some linear step-growth polymers, and three-dimensional network step-growth polymers. (JN)

Stille, J. K.

1981-01-01

297

Halley's polymeric organic molecules  

SciTech Connect

The detection of polymeric organic compounds in the mass spectrum of Comet Halley obtained with the Positive Ion Cluster Composition analyzer on Giotto are examined. It is found that, in addition to polyoxymethylene, other polymers and complex molecules may exist in the comet. It is suggested that polymerized hydrogen cyanide may be a source for the observed CN and NH2 jets. 31 refs.

Huebner, W.F.; Boice, D.C.; Korth, A.

1989-01-01

298

Halley's polymeric organic molecules  

NASA Technical Reports Server (NTRS)

The detection of polymeric organic compounds in the mass spectrum of Comet Halley obtained with the Positive Ion Cluster Composition analyzer on Giotto are examined. It is found that, in addition to polyoxymethylene, other polymers and complex molecules may exist in the comet. It is suggested that polymerized hydrogen cyanide may be a source for the observed CN and NH2 jets.

Huebner, W. F.; Boice, D. C.; Korth, A.

1989-01-01

299

Controlled graft copolymerization of lactic acid onto starch in a supercritical carbon dioxide medium.  

PubMed

This work presents a new approach for the synthesis of a starch-g-poly L-lactic acid (St-g-PLA) copolymer via the graft copolymerization of LA onto starch using stannous 2-ethyl hexanoate (Sn(Oct)2) as a catalyst in a supercritical carbon dioxide (scCO2) medium. The effects of several process parameters, including the pressure, temperature, scCO2 flow rate and reaction time, on the polymerization yield and grafting degree were studied. Amorphous graft St-g-PLA copolymers with increased thermal stability and processability were produced with a high efficiency. The maximum grafting degree (i.e., 52% PLA) was achieved with the following reaction conditions: 6h, 100°C, 200 bar and a 1:3 (w/w) ratio of St/LA. It was concluded that these low cost biobased graft biopolymers are potential candidates for several environment-friendly applications. PMID:25263875

Salimi, Kouroush; Yilmaz, Mehmet; Rzayev, Zakir M O; Piskin, Erhan

2014-12-19

300

Preparation of poly (methyl methacrylate)\\/nanometer calcium carbonate composite by in-situ emulsion polymerization  

Microsoft Academic Search

Methyl methacrylate (MMA) emulsion polymerization in the presence of nanometer calcium carbonate (nano-CaCO3) surface modified with ?-methacryloxypropyltrimethoxysilane (MPTMS) was carried out to prepare poly (methyl methacrylate)\\u000a (PMMA)\\/nano-CaCO3 composite. The reaction between nano-CaCO3 and MPTMS, and the grafting of PMMA onto nano-CaCO3 were confirmed by infrared spectrum. The grafting ratio and grafting efficiency of PMMA on nano-CaCO3 modified with MPTMS were

Shi Jian-ming; Bao Yong-zhong; Huang Zhi-ming; Weng Zhi-xue

2004-01-01

301

synthesis of novel four armed PE-PCL grafted superparamagnetic and biocompatible nanoparticles.  

PubMed

Novel biocompatible polymer immobilized superparamagnetic nanoparticles (MNP) are prepared by grafting four armed pentaerythritol poly(?-polycaprolactone) (PE-PCL) onto silane modified MNP. The MNPs are synthesized by hydrothermal process and its modification using (3-aminopropyl)trimethoxysilane (TMAS) coating is done by the sol-gel technique. The pentaerythritol (PE) initiated ring-opening polymerization (ROP) is carried out to prepare four armed PE-PCL. The reaction is shown to follow first order kinetics. The structure of PE-PCL is confirmed by NMR spectrum and MALDI-TOF analysis. The in situ grafting of PE-PCL onto modified MNP has been carried out by using 4,4'-methylenediphenyl diisocyanate (MDI) as an intermediate linker. The grafting density as determined by TGA analysis has been found to be significantly higher than previously reported linear PCL grafted MNPs in the literature. This leads to uniform dispersion of grafted MNPs which still is a challenging task in contemporary research. The effective dispersion of MNP into PE-PCL matrix is analyzed by HRTEM. The saturation magnetization of the PE-PCL grafted MNPs is significantly high and this can be tailored further by varying the grafting density. The biocompatibility of polymer grafted nanoparticles is confirmed by MTT assay using HeLa cell line. The superparamagnetic and biocompatible novel PE-PCL grafted MNP so prepared would have manifold potential applications including in therapy and targeted drug delivery. PMID:24041315

Panja, Sudipta; Saha, Biswajit; Ghosh, S K; Chattopadhyay, Santanu

2013-10-01

302

Treatment of oil in water emulsions by ceramic-supported polymeric membranes  

SciTech Connect

A novel membrane was developed by growing polymer chains from the surface of a porous ceramic support, resulting in a composite membrane which combines the mechanical properties of the inorganic membrane with the selective interactions of the polymer. The configuration of the grafted polymer brush layer is determined by solvent-polymer interactions, with a hydrophilic polymer being stretched away from the surface by aqueous solutions and collapsed against the surface by organic solvents. This behavior of the grafted chains provides Ceramic-Supported Polymeric (CSP) membranes with unique properties for certain water treatment applications. One application envisioned for these CSP membranes, in which the selectivity is influenced by interactions between the solvent and the grafted polymer, is the cross-flow filtration of an oil-in-water emulsion. In this case, a hydrophilic grafted Polyvinylpyrrolidone (PVP) brush layer expanded into the pore volume due to the affinity of the polymer for water. These extended grafted chains preferentially allow the passage of water over oil, producing a permeate stream with a lower total organic carbon content compared to an unmodified membrane. Another advantage of the CSP membrane is in reducing permeate flux decline believed to be caused by the adsorption of oil onto the membrane surface. For the PVP-modified CSP membrane, the grafted polymer alters the membrane surface character from hydrophobic to hydrophilic, reducing the tendency for oil adsorption. This phenomenon was demonstrated by comparison of permeate flow rate behavior for both unmodified and graft polymerized (CSP) membranes.

Castro, R.P.; Cohen, Y.; Monbouquette, H.G. [Univ. of California, Los Angeles, CA (United States). Dept. of Chemical Engineering

1994-12-31

303

Synthesis of novel size exclusion chromatography support by surface initiated aqueous atom transfer radical polymerization.  

PubMed

We report the use of aqueous surface-initiated atom transfer radical polymerization (SI-ATRP) to grow polymer brushes from a "gigaporous" polymeric chromatography support for use as a novel size exclusion chromatography medium. Poly(N,N-dimethylacrylamide) (PDMA) was grown from hydrolyzable surface initiators via SI-ATRP catalyzed by 1,1,4,7,10,10-hexamethyltriethylenetetramine (HMTETA)/CuCl. Grafted polymer was characterized semiquantitatively by ATR-FTIR and also cleaved and quantitatively characterized for mass, molecular weight, and polydispersity via analytical SEC/MALLS. The synthesis provides control over graft density and allows the creation of dense brushes. Incorporation of negative surface charge was found to be crucial for improving the initiation efficiency. As polymer molecular weight and density could be controlled through reaction conditions, the resulting low-polydispersity grafted polymer brush medium is shown to be suitable for use as a customizable size exclusion chromatography medium for investigating the principals of entropic interaction chromatography. All packed media investigated showed size-dependent partitioning of solutes, even for low graft density systems. Increasing the molecular weight of the grafts allowed solutes more access to the volume fraction in the column available for partitioning. Compared to low graft density media, increased graft density caused eluted solute probes to be retained less within the column and allowed for greater size discrimination of probes whose molecular weights were less than 10(4) kDa. PMID:17924673

Coad, Bryan R; Kizhakkedathu, Jayachandran N; Haynes, Charles A; Brooks, Donald E

2007-11-01

304

Multiphase Polymeric Materials  

NSDL National Science Digital Library

Developed by a group of PhD students at the University of Southern Mississippi, the Multiphase Polymeric Materials Website presents both general information about composites and current research on multiphase polymeric materials, including information about blends, coatings, and nanocomposites. As the newest addition to Macrogalleria (described in the March 31, 1999 Scout Report for Science & Engineering), the Multiphase Polymeric Materials Website includes information on Composites in General, Composites, Characterization and Analysis, and Application. Most useful to researchers, the Application section introduces the relationship between polymer composites and component level electronics with examples such as PCB Construction, Encapsulation of Integrated Circuits, and Non-Conductive Adhesives.

305

Impact of reaction conditions on architecture and rheological properties of starch graft polyacrylamide polymers  

Technology Transfer Automated Retrieval System (TEKTRAN)

We carried out experiments examining the impact that solvent selection and reaction conditions have on the radical initiated graft polymerization reaction of acrylamide onto starch. We have also evaluated the rheological properties the starch graftpolyacrylamide product when a gel is formed in water...

306

Grafting thermosensitive PNIPAM onto the surface of carbon spheres  

NASA Astrophysics Data System (ADS)

Thermosensitive polymer poly(N-isopropylacrylamine) (PNIPAM) grafted-carbon spheres (CSs) composites were synthesized and investigate the influence of synthesis parameters on phase transition temperature in order to produce thermosensitive composites with different phase transition temperatures, which may be applied to different application fields. First, vinyl groups were introduced onto the surface of CSs by mixed acid oxidation and reacting with 3-methacryloxypropyl trimethoxysilane. Then, PNIPAM was grafted onto the surface of CSs by surface free-radical polymerization. According to the differential scanning calorimetric analysis, the PNIPAM-grafted CSs composites are temperature responsive. The weight ratio of monomer to CSs and the initiator dosage had great influence on the polymer shell thickness and the lower critical solution temperature (LCST) of the composites determined by the number of grafted polymer chain, chain length and the cross-link degree. The polymer shell thickness and the LCST of the composites increased with the increase of the amount of monomer in proper range, however, first increase and then decrease with the increasing initiator dosage. The cross-linking agent content affects critically the cross-link degree, and then the LCST. Therefore, the LCST of the PNIPAM-grafted CSs composites was adjustable by changing the synthesis parameters, which lays the basis for CSs application in different fields.

Guo, Xingmei; Du, Zefeng; Song, Maoning; Qiu, Li; Shen, Yinghua; Yang, Yongzhen; Liu, Xuguang

2014-12-01

307

Space environmental effects on polymeric materials  

NASA Technical Reports Server (NTRS)

Two of the major environmental hazards in the Geosynchronous Earth Orbit (GEO) are energetic charged particles and ultraviolet radiation. The charged particles, electrons and protons, range in energy from 0.1 to 4 MeV and each have a flux of 10 to the 8th sq cm/sec. Over a 30 year lifetime, materials in the GEO will have an absorbed dose from this radiation of 10 to the 10th rads. The ultraviolet radiation comes uninhibited from the sun with an irradiance of 1.4 kw/sq m. Radiation is known to initiate chain sission and crosslinking in polymeric materials, both of which affect their structural properties. The 30-year dose level from the combined radiation in the GEO exceeds the threshold for measurable damage in most polymer systems studied. Of further concern is possible synergistic effects from the simultaneous irradiation with charged particles and ultraviolet radiation. Most studies on radiation effects on polymeric materials use either electrons or ultraviolet radiation alone, or in a sequential combination.

Kiefer, Richard L.; Orwoll, Robert A.

1988-01-01

308

PREFACE: IUMRS-ICA 2008 Symposium, Sessions 'X. Applications of Synchrotron Radiation and Neutron Beam to Soft Matter Science' and 'Y. Frontier of Polymeric Nano-Soft-Materials - Precision Polymer Synthesis, Self-assembling and Their Functionalization'  

NASA Astrophysics Data System (ADS)

Applications of Synchrotron Radiation and Neutron Beam to Soft Matter Science (Symposium X of IUMRS-ICA2008) Toshiji Kanaya, Kohji Tashiro, Kazuo Sakura Keiji Tanaka, Sono Sasaki, Naoya Torikai, Moonhor Ree, Kookheon Char, Charles C Han, Atsushi Takahara This volume contains peer-reviewed invited and contributed papers that were presented in Symposium X 'Applications of Synchrotron Radiation and Neutron Beam to Soft Matter Science' at the IUMRS International Conference in Asia 2008 (IUMRS-ICA 2008), which was held on 9-13 December 2008, at Nagoya Congress Center, Nagoya, Japan. Structure analyses of soft materials based on synchrotron radiation (SR) and neutron beam have been developed steadily. Small-angle scattering and wide-angle diffraction techniques clarified the higher-order structure as well as time dependence of structure development such as crystallization and microphase-separation. On the other hand, reflectivity, grazing-incidence scattering and diffraction techniques revealed the surface and interface structural features of soft materials. From the viewpoint of strong interests on the development of SR and neutron beam techniques for soft materials, the objective of this symposium is to provide an interdisciplinary forum for the discussion of recent advances in research, development, and applications of SR and neutron beams to soft matter science. In this symposium, 21 oral papers containing 16 invited papers and 14 poster papers from China, India, Korea, Taiwan, and Japan were presented during the three-day symposium. As a result of the review of poster and oral presentations of young scientists by symposium chairs, Dr Kummetha Raghunatha Reddy (Toyota Technological Institute) received the IUMRS-ICA 2008 Young Researcher Award. We are grateful to all invited speakers and many participants for valuable contributions and active discussions. Organizing committee of Symposium (IUMRS-ICA 2008) Professor Toshiji Kanaya (Kyoto University) Professor Kohji Tashiro (Toyota Technological Institute) Professor Kazuo Sakurai(Kitakyushu University) Professor Keiji Tanaka (Kyushu University) Dr Sono Sasaki (JASRI/Spring-8) Professor Naoya Torikai (KENS) Professor Moonhor Ree (POSTECH) Professor Kookheon Char (Seoul National University) Professor Charles C Han (CAS) Professor Atsushi Takahara(Kyushu University) Frontier of Polymeric Nano-Soft-Materials, Precision Polymer Synthesis, Self-assembling and Their Functionalization (Symposium Y of IUMRS-ICA2008) Seiichi Kawahara, Rong-Ming Ho, Hiroshi Jinnai, Masami Kamigaito, Takashi Miyata, Hiroshi Morita, Hideyuki Otsuka, Daewon Sohn, Keiji Tanaka It is our great pleasure and honor to publish peer-reviewed papers, presented in Symposium Y 'Frontier of Polymeric Nano-Soft-Materials Precision Polymer Synthesis, Self-assembling and Their Functionalization' at the International Union of Materials Research Societies International Conference in Asia 2008 (IUMRS-ICA2008), which was held on 9-13 December 2008, at Nagoya Congress Center, Nagoya, Japan. 'Polymeric nano-soft-materials' are novel outcomes based on a recent innovative evolution in polymer science, i.e. precision polymer synthesis, self-assembling and functionalization of multi-component systems. The materials are expected to exhibit specific functions and unique properties due to their hierarchic morphologies brought either by naturally-generated ordering or by artificial manipulation of the systems, e.g., crystallization and phase-separation. The emerging precision synthesis has brought out new types of polymers with well-controlled primary structures. Furthermore, the surface and interface of the material are recognized to play an important role in the outstanding mechanical, electrical and optical properties, which are required for medical and engineering applications. In order to understand structure-property relationships in the nano-soft-materials, it is indispensable to develop novel characterization techniques. Symposium Y aimed to provide recent advances in polymer synthesis, self-assembling processes and morpholog

Takahara, Atsushi; Kawahara, Seiichi

2009-09-01

309

Surface modification of polymeric biomaterials with poly(ethylene oxide), albumin, and heparin for reduced thrombogenicity  

Microsoft Academic Search

Appropriate surface modification has significantly improved the blood compatibility of polymeric biomaterials. This article reviews methods of surface modification with water-soluble polymers, such as polyethylene oxide (PEO), albumin, and heparin. PEO is a synthetic, neutral, watersoluble polymer, while albumin and heparin are a natural globular protein and an anionic polysaccharide, respectively. When grafted onto the surface, all three macromolecules share

Mansoor Amiji

1993-01-01

310

Thermally Polymerized Rylene Nanoparticles  

E-print Network

Rylene dyes functionalized with varying numbers of phenyl trifluorovinyl ether (TFVE) moieties were subjected to a thermal emulsion polymerization to yield shape-persistent, water-soluble chromophore nanoparticles. Perylene ...

Andrew, Trisha Lionel

311

Rib grafts in septorhinoplasty.  

PubMed

Autogenous cartilage has generally been considered the gold standard grafting material in reconstructive septorhinoplasty for volume filling and structural support. In the restructuring of the nasal skeleton, autogenous cartilage can be harvested from the nasal septum, the auricle or the rib, but costal cartilage is considered the best graft material in patients requiring major reconstruction. Rib cartilage is an outstanding material in reconstructive septorhinoplasty, especially in revision surgery and when large amounts of tissue are required. This autologous material has a low rate of complications such as resorption, infection and extrusion compared to homografts and alloplastic implants. In the present study, the authors analyze and discuss the use of autogenous rib cartilage in 54 patients who underwent primary and revision septorhinoplasty. Its use is also suggested in cases in which there is a need to have a fair amount of cartilaginous tissue to be grafted for nasal framework reconstruction and respiratory function improvement. PMID:23853415

Moretti, A; Sciuto, S

2013-06-01

312

Tailoring the properties of thermoplastic starch by blending with cinnamyl alcohol and radiation processing: An insight into the competitive grafting and scission reactions  

NASA Astrophysics Data System (ADS)

The present paper focuses on the effects of electron beam (EB) irradiation on thermoplastic materials based on destructurized starch including glycerol and water as plasticizers to assess the potentiality of cinnamyl alcohol as reactive additive capable of counterbalancing the degradation of the polysaccharide by inducing interchain covalent linkages. The tensile properties at break of test specimens of controlled composition submitted to EB irradiation at doses ranging from 50 to 200 kGy revealed the presence of competitive chain scission and bridging in samples containing cinnamyl alcohol at a relative concentration of 2.5% with regard to dry starch. The occurrence of crosslinking under particular conditions was evidenced by gel fraction measurements. The treatment under radiation was also applied to model blends including maltodextrin as a model for starch and the other ingredients to gain an insight into the radiation induced mechanisms at the molecular level. The presence of cinnamyl alcohol is found to limit degradation. Size exclusion chromatography and gel fraction allowed to monitor the effects and confirmed unambiguously the attachment of UV-absorbing chromophores onto the maltodextrin main chain. The combination of the obtained results demonstrates the possibility of altering in a favorable way the tensile properties of plasticized starch by applying high energy radiation to properly formulated blends including aromatic compounds like cinnamyl alcohol.

Khandal, Dhriti; Mikus, Pierre-Yves; Dole, Patrice; Bliard, Christophe; Soulestin, Jérémie; Lacrampe, Marie-France; Baumberger, Stéphanie; Coqueret, Xavier

2012-08-01

313

Electron Beam Technologies for Preparation of Polymeric Materials Used for Waste Water Treatment, Agriculture, and Medicine  

Microsoft Academic Search

Radiation research results in the field of polymeric materials, obtained in the last few years by electron beam irradiation of aqueous solutions containing appropriate monomer mixtures, such as acrylamide, acrylic acid and vinyl acetate, are presented. Two types of polymeric flocculants for waste water treatment and three kinds of hydrogels for agriculture and medicine are described. The effects of radiation

D. Martin; M. Radoiu; M. Dragusin; R. Cramariuc; I. Indreias; C. Oproiu; S. Marghitu; A. Manea; M. Toma; V. Bestea

1999-01-01

314

Grafting effects on vegetable quality  

Technology Transfer Automated Retrieval System (TEKTRAN)

In the United States, vegetable grafting is rare and few experiments have been done to determine optimal grafting procedures and production practices for different geographical and climatic regions in America. Grafting vegetables to control soilborne disease is a common practice in Asia, parts of E...

315

Bone Grafts in Craniofacial Surgery  

PubMed Central

Reconstruction of cranial and maxillofacial defects is a challenging task. The standard reconstruction method has been bone grafting. In this review, we shall describe the biological principles of bone graft healing, as pertinent to craniofacial reconstruction. Different types and sources of bone grafts will be discussed, as well as new methods of bone defect reconstruction. PMID:22110806

Elsalanty, Mohammed E.; Genecov, David G.

2009-01-01

316

Accompanying of parameters of color, gloss and hardness on polymeric films coated with pigmented inks cured by different radiation doses of ultraviolet light  

NASA Astrophysics Data System (ADS)

In the search for alternatives to traditional paint systems solvent-based, the curing process of polymer coatings by ultraviolet light (UV) has been widely studied and discussed, especially because of their high content of solids and null emission of VOC. In UV-curing technology, organic solvents are replaced by reactive diluents, such as monomers. This paper aims to investigate variations on color, gloss and hardness of print inks cured by different UV radiation doses. The ratio pigment/clear coating was kept constant. The clear coating presented higher average values for König hardness than pigmented ones, indicating that UV-light absorption has been reduced by the presence of pigments. Besides, they have indicated a slight variation in function of cure degree for the studied radiation doses range. The gloss loss related to UV light exposition allows inferring that some degradation occurred at the surface of print ink films.

Bardi, Marcelo Augusto Gonçalves; Machado, Luci Diva Brocardo

2012-09-01

317

Theoretical study on tethered polymers with explicit grafting points in ?-solvent  

NASA Astrophysics Data System (ADS)

Systematic studies on the polymers chemically grafted onto a solid substrate with various grafting densities are presented based on the self-consistent mean-field theory (SCMFT). The distribution of the grafting points is explicitly included and all the three coordinates of each grafting point are fixed during the calculations. The existence of solvent molecules is also explicitly considered in the model and the case of ?-solvent is investigated. The structure of the system is derived by solving the SCMFT equations in three-dimensional space. For the cases of low grafting density, the system is highly inhomogeneous and typical mushroom-like structures are derived. On the other hand, when the grafting density is high enough, the system is nearly homogeneous along the substrate and the polymer concentration profile is consistent with the numerical results of one dimensional SCMFT calculations. The crossover between "mushroom" regime and polymer brush is obtained by tuning the grafting density. In addition, in brush limit, while the root-mean-squared thickness of the brush is linearly dependent on the degree of polymerization, its dependency on the grafting density is in general more complicated than a simple power law.

Suo, Tongchuan; Yan, Dadong

2011-02-01

318

Mixing in polymeric microfluidic devices.  

SciTech Connect

This SAND report describes progress made during a Sandia National Laboratories sponsored graduate fellowship. The fellowship was funded through an LDRD proposal. The goal of this project is development and characterization of mixing strategies for polymeric microfluidic devices. The mixing strategies under investigation include electroosmotic flow focusing, hydrodynamic focusing, physical constrictions and porous polymer monoliths. For electroosmotic flow focusing, simulations were performed to determine the effect of electroosmotic flow in a microchannel with heterogeneous surface potential. The heterogeneous surface potential caused recirculations to form within the microchannel. These recirculations could then be used to restrict two mixing streams and reduce the characteristic diffusion length. Maximum mixing occurred when the ratio of the mixing region surface potential to the average channel surface potential was made large in magnitude and negative in sign, and when the ratio of the characteristic convection time to the characteristic diffusion time was minimized. Based on these results, experiments were performed to evaluate the manipulation of surface potential using living-radical photopolymerization. The material chosen to manipulate typically exhibits a negative surface potential. Using living-radical surface grafting, a positive surface potential was produced using 2-(Dimethylamino)ethyl methacrylate and a neutral surface was produced using a poly(ethylene glycol) surface graft. Simulations investigating hydrodynamic focusing were also performed. For this technique, mixing is enhanced by using a tertiary fluid stream to constrict the two mixing streams and reduce the characteristic diffusion length. Maximum mixing occurred when the ratio of the tertiary flow stream flow-rate to the mixing streams flow-rate was maximized. Also, like the electroosmotic focusing mixer, mixing was also maximized when the ratio of the characteristic convection time to the characteristic diffusion time was minimized. Physical constrictions were investigated through simulations. The results show that the maximum mixing occurs when the height of the mixing region is minimized. Finally, experiments were performed to determine the effectiveness of using porous polymer monoliths to enhance mixing. The porous polymer monoliths were constructed using a monomer/salt paste. Two salt crystal size ranges were used; 75 to 106 microns and 53 to 180 microns. Mixing in the porous polymer monoliths fabricated with the 75 to 106 micron salt crystal size range was six times higher than a channel without a monolith. Mixing in the monolith fabricated with the 53 to 180 micron salt crystal size range was nine times higher.

Schunk, Peter Randall; Sun, Amy Cha-Tien; Davis, Robert H. (University of Colorado at Boulder, Boulder, CO); Brotherton, Christopher M. (University of Colorado at Boulder, Boulder, CO)

2006-04-01

319

Synthesis and characterization of nanocomposite organic/inorganic hybrid materials using living cationic polymerization  

NASA Astrophysics Data System (ADS)

A series of novel chlorosilyl functional initiators have been prepared and applied for the first time in the living cationic polymerization of isobutylene (IB). Well-defined polyisobutylenes (PIBs) carrying mono-, di-, and trichlorosilyl head-group, and a tert-chloro end-group were synthesized using newly designed silyl-functional initiators in conjunction with TiCl4 in Hex:MeCl (60:40, v:v) at -80°C. End-group analysis by 1H NMR spectroscopy verified the product structure and the survival of the Si-Cl head-groups during the polymerization. The chlorosilyl functional initiators and chlorosilyl functional PIBs have been employed for the synthesis of PIB brushes on planar silicate substrates by the "grafting from" and "grafting to" techniques. Structurally well-defined polymer/inorganic nanocomposites were prepared by surface-initiated living cationic polymerization of isobutylene (IB). The living cationic polymerization of IB was initiated from initiators self-assembled on the surface of silica nanoparticles in the presence of additional soluble "free initiator" with TiCl4 in hexanes/CH3Cl (60/40, v/v) at -80°C. The polymerization displayed the diagnostic criteria for living cationic polymerization and provided densely grafted polymers of controlled molecular weight with an approximate graft density of 3.3 chains/nm 2. The surface-initiated polymerization of IB without added "free initiator" also yielded grafted polymer chains with good molecular weight control and narrow molecular weight distribution (Mw/M n). A series of novel hybrid poly(styryl-POSS), poly(isobutylene- b-(styryl-POSS)), and poly(isobutylene-b-(styryl-POSS)- b-isobutylene) are synthesized and characterized. Living cationic polymerization of styryl-POSS macromer was carried out using the 1-chloro-1-(4-methyphenyl)ethane (p-MeStCl)/TiCl4/MeChx:CH3Cl (60:40, v:v)/-80°C system in the presence of DTBP. Using these conditions, we have synthesized AB diblock, and ABA linear triblock copolymers containing polyisobutylene (PIB)-based rubbery mid block (B) with amorphous glassy poly(styryl-POSS) end blocks (A) by living cationic polymerization using sequential monomer addition. Well-defined PIB-b-P(styryl-POSS) and PIB- b-P(styryl-POSS)-b-PIB have been successfully prepared. The styryl-POSS based hybrid polymers were characterized by thermogravimetry and GPC measurements. (Abstract shortened by UMI.)

Kim, Iljin

320

Slicing, skinning, and grafting  

E-print Network

We prove that a Bers slice is never algebraic, meaning that its Zariski closure in the character variety has strictly larger dimension. A corollary is that skinning maps are never constant. The proof uses grafting and the theory of complex projective structures.

Dumas, David

2007-01-01

321

Silicon tetrachloride plasma induced grafting for starch-based composites  

NASA Astrophysics Data System (ADS)

Non-modified virgin starch is seldom used directly in industrial applications. Instead, it is often physically and/or chemically modified to achieve certain enhanced properties. For many of the non-food applications, these modifications involve changing its hydrophilicity to create hydrophobic starch. In this study, the hydrophobic starch was produced through silicon tetrachloride (SiCl4) plasma induced graft polymerization, so that it could be used as a renewable and biodegradable component of, or substitute for, the petrochemical-based plastics. It was suggested that this starch graft-copolymer might be used as reinforcing components in silicone-rubber materials for starch-based composites. To make this starch graft-copolymer, the ethyl ether-extracted starch powders were surface functionalized by SiCl4 plasma using a 13.56 MHz radio frequency rotating plasma reactor and subsequently stabilized by either ethylene diamine or dichlorodimethylsilane (DCDMS). The functionalized starch was then graft-polymerized with DCDMS to form polydimethylsiloxane (PDMS) layers around the starch granules. The presence of this PDMS layer was demonstrated by electron spectroscopy for chemical analysis (ESCA/XPS), Fourier transform infrared spectroscopy (FTIR), scanning electron microscopy (SEM), gas chromatography-mass spectroscopy (GC-MS), thermo gravimetry/differential thermal analysis (TG/DTA), and other analyses. It was shown that the surface morphology, thermal properties, swelling characteristic, and hydrophilicity of starch were all changed due to the existence of this protective hydrophobic PDMS layer. Several different procedures to carry out the functionalization and graft polymerization steps were evaluated to improve the effectiveness of the reactions and to prevent the samples from being hydrolyzed by the grafting byproduct HCl. Actinometry, GC-MS, and residual gas analyzer (RGA) were used to investigate the mechanisms of the SiCl4 discharge and to optimize the plasma modification. These plasma diagnostic results showed that, to achieve better plasma modification, higher plasma power and lower SiCl4 vapor pressure would be needed; however, it was found that the efficiency of the modification peaked at a certain point of plasma treatment time (˜10 minutes) and there was not much subsequent improvement with prolonged plasma treatment.

Ma, Yonghui C.

322

Surface initiated polymerization on pulsed plasma deposited polyallylamine: a polymer substrate-independent strategy to soft surfaces with polymer brushes.  

PubMed

The deposition of polyallylamine (PAA) adlayers by pulsed plasma polymerization on various types of polymeric substrates has been explored as a general route to amino functionalized polymeric surfaces. These amino groups are highly suitable for anchoring an atom transfer radical polymerization (ATRP) initiator via a robust amide linkage. Subsequent surface initiated ATRP (SI-ATRP) of monomethoxy oligo(ethylene glycol) methacrylate (MeOEGMA) resulted in polyMeOEGMA brush grafted polymer surfaces. This combined strategy of pulsed plasma polymerization with SI-ATRP was demonstrated for five different polymeric substrates namely polyether ether ketone (PEEK), polyethylene terephthalate (PET), polyimide (PI), polypropylene (PP), and polytetrafluoroethylene (PTFE). Analysis of brush layers by attenuated total reflection infrared (ATR-IR) spectroscopy as well as X-ray photoelectron spectroscopy (XPS) fully corroborated the success of the proposed strategy for all substrate types. PMID:21858892

Yameen, Basit; Khan, Hadayat Ullah; Knoll, Wolfgang; Förch, Renate; Jonas, Ulrich

2011-11-01

323

Plasma polymerized high energy density dielectric films for capacitors  

NASA Technical Reports Server (NTRS)

High energy density polymeric dielectric films were prepared by plasma polymerization of a variety of gaseous monomers. This technique gives thin, reproducible, pinhole free, conformable, adherent, and insoluble coatings and overcomes the processing problems found in the preparation of thin films with bulk polymers. Thus, devices are prepared completely in a vacuum environment. The plasma polymerized films prepared all showed dielectric strengths of greater than 1000 kV/cm and in some cases values of greater than 4000 kV/cm were observed. The dielectric loss of all films was generally less than 1% at frequencies below 10 kHz, but this value increased at higher frequencies. All films were self healing. The dielectric strength was a function of the polymerization technique, whereas the dielectric constant varied with the structure of the starting material. Because of the thin films used (thickness in the submicron range) surface smoothness of the metal electrodes was found to be critical in obtaining high dielectric strengths. High dielectric strength graft copolymers were also prepared. Plasma polymerized ethane was found to be thermally stable up to 150 C in the presence of air and 250 C in the absence of air. No glass transitions were observed for this material.

Yamagishi, F. G.

1983-01-01

324

Thermally and photoinduced polymerization of ultrathin sexithiophene films  

SciTech Connect

The thermally-induced polymerization of ?-sexithiophene (6T) molecules on Ag(001) and Au(001) gives rise to long unbranched polymer chains or branched polymer networks depending on the annealing parameters. There, the onset temperature for polymerization depends on the strength of interaction with the underlying substrate. Similar polymerization processes are also induced by ultraviolet radiation with photon energies between 3.0 and 4.2 eV. Radical formation by an electronic excitation in the 6T molecule is proposed as the driving mechanism that necessitates the interplay with the metallic substrate.

Sander, Anke; Hammer, Rene; Duncker, Klaus; Förster, Stefan [Institute of Physics, Martin-Luther-Universität Halle-Wittenberg, Von-Danckelmann-Platz 3, 06120 Halle(Saale) (Germany); Widdra, Wolf, E-mail: wolf.widdra@physik.uni-halle.de [Institute of Physics, Martin-Luther-Universität Halle-Wittenberg, Von-Danckelmann-Platz 3, 06120 Halle(Saale) (Germany); Max Planck Institute of Microstructure Physics, Weinberg 2, 06120 Halle(Saale) (Germany)

2014-09-14

325

Preparation and characterization of poly(isobutyl methacrylate) microbeads with grafted amidoxime groups  

NASA Astrophysics Data System (ADS)

Poly(isobutyl methacrylate) (PiBMA) microspheres with a 800- to 1500-?m diameter range synthesized by suspension polymerization technique were used as the trunk polymer in the preparation of a highly efficient new adsorbent. Glycidyl methacrylate (GMA) was grafted onto the trunk polymer by pre-irradiation grafting technique. Grafting conditions were optimized, and GMA grafted PiBMA beads were modified with iminodiacetonitrile (IDAN) in ethanol at 80 °C. The nitrile groups were then amidoximated by using 6% (m/v) hydroxylamine hydrochloride in methanol solution. The IDAN modification and the conversion of the nitrile groups to amidoxime were followed by FT-IR spectroscopy. The surface morphology and thermal behavior of the PiBMA and its modificated forms were also characterized by scanning electron microscopy (SEM) and thermogravimetric analysis (TGA) and differential scanning calorimetry (DSC) techniques further confirming modification and amidoximation.

Çaykara, Tuncer; Alaslan, ?erife ?irin; Gürü, Metin; Bodugöz, Hatice; Güven, Olgun

2007-10-01

326

CASE REPORT Pharyngocutaneous Fistula Closure Using Autologous Fat Grafting  

PubMed Central

Objective: Although the majority of pharyngocutaneous fistulas close spontaneously with conservative measures, 20% to 30% of patients do not respond to this approach, thereby necessitating major reconstruction with adjacent or free tissue transfers. These procedures carry considerable risk, particularly in patients with medical comorbidities or a history of prior surgery/radiation. Less invasive treatment approaches designed to reverse tissue damage or promote spontaneous healing would represent an important medical advance. Autologous fat grafts have been previously shown to promote healing of persistent wounds and improve the quality of radiation-damaged tissue. In this report, successful closure of a persistent pharyngocutaneous fistula with use of autologous fat grafting is described. Method: The history and details of pharyngocutaneous fistula closure in a patient with recurrent head and neck cancer are reported. Result: A 67-year-old patient with recurrent head and neck cancer and prior radiotherapy underwent reresection including partial pharyngectomy with pectoralis major myocutaneous flap closure. Postoperatively, he developed an enterocutaneous fistula, which failed to close with conservative measures including 8 months of nothing per os. Two rounds of autologous fat grafting were performed with successful fistula healing. Conclusion: Autologous fat grafting is a useful treatment for closure of persistent pharyngocutaneous fistulas. Autologous fat grafting should be considered in poor surgical candidates, particularly in the setting of extensive radiation-induced tissue damage. PMID:23691260

Hespe, Geoffrey E.; Albornoz, Claudia R.; Mehrara, Babak J.; Kraus, Dennis; Matros, Evan

2013-01-01

327

Dead Sea Minerals loaded polymeric nanoparticles.  

PubMed

Therapeutic properties of Dead Sea Water (DSW) in the treatment of skin diseases such as atopic dermatitis, psoriasis and photo aging UV damaged skin have been well established. DSW is in fact rich in minerals such as calcium, magnesium, sodium, potassium, zinc and strontium which are known to exploit anti-inflammatory effects and to promote skin barrier recovery. In order to develop a Dead Sea Minerals (DSM) based drug delivery system for topical therapy of skin diseases, polymeric nanoparticles based on Poly (maleic anhydride-alt-butyl vinyl ether) 5% grafted with monomethoxy poly(ethyleneglycol) 2000 MW (PEG) and 95% grafted with 2-methoxyethanol (VAM41-PEG) loaded with DSM were prepared by means of a combined miniemulsion/solvent evaporation process. The resulting nanoparticles were characterized in terms of dimension, morphology, biocompatibility, salt content and release. Cytocompatible spherical nanoparticles possessing an average diameter of about 300 nm, a time controlled drug release profile and a high formulation yield were obtained. PMID:21676600

Dessy, Alberto; Kubowicz, Stephan; Alderighi, Michele; Bartoli, Cristina; Piras, Anna Maria; Schmid, Ruth; Chiellini, Federica

2011-10-15

328

Self-assembled structures of hydrogen-bonded poly(vinyl chloride-g-4-vinyl pyridine) graft copolymers  

Microsoft Academic Search

An amphiphilic graft copolymer of poly(vinyl chloride-graft-4-vinyl pyridine), i.e., PVC-g-P4VP was synthesized via atom transfer radical polymerization (ATRP) and modified by introducing 1,5-dihydroxynaphthalene (DHN) as a hydrogen bonding donor to form hydrogen-bonded macromolecules. The PVC-g-P4VP graft copolymer prepared from a selective solvent for PVC, i.e., tetrahydrofuran (THF) exhibited a well-organized micellar morphology consisting of a P4VP core and a PVC

Joo Hwan Koh; Jin Ah Seo; Jong Kwan Koh; Jong Hak Kim

2010-01-01

329

Studies in reactive extrusion processing of biodegradable polymeric materials  

NASA Astrophysics Data System (ADS)

Various reaction chemistries such as Polymerization, Polymer cross-linking and Reactive grafting were investigated in twin-screw extruders. Poly (1,4-dioxan-2-one) (PPDX) was manufactured in melt by the continuous polymerization of 1,4-dioxan-2-one (PDX) monomer in a twin-screw extruder using Aluminum tri-sec butoxide (ATSB) initiator. Good and accurate control over molecular weight was obtained by controlling the ratio of monomer to initiator. A screw configuration consisting of only conveying elements was used for the polymerization. The polymerization reaction was characterized by a monomer-polymer dynamic equilibrium, above the melting temperature of the polymer, limiting the equilibrium conversion to 78-percent. Near complete (˜100-percent) conversion was obtained on co-polymerizing PDX monomer with a few mol-percent (around 8-percent) Caprolactone (CL) monomer in a twin-screw extruder using ATSB initiator. The co-polymers exhibited improved thermal stability with reduction in glass transition temperature. The extruder was modeled as an Axial Dispersed Plug Flow Reactor for the polymerization of CL monomer using Residence Time Distribution (RTD) Analysis. The model provided a good fit to the experimental RTD and conversion data. Aliphatic and aliphatic-aromatic co-polyesters, namely Polycaprolactone (PCL) and Poly butylenes (adipate-co-terephthalate) (Ecoflex) were cross-linked in a twin-screw extruder using radical initiator to form micro-gel reinforced biodegradable polyesters. Cross-linked Ecoflex was further extrusion blended with talc to form blends suitable to be blown into films. A screw configuration consisting of conveying and kneading elements was found to be effective in dispersion of the talc particles (5--10 microns) in the polyester matrix. While the rates of crystallization increased for the talc filled polyester blends, overall crystallinity reduced. Mechanical, tear and puncture properties of films made using the talc filled polyester blends were comparable to linear low density Polyethylene (LDPE). Ecoflex-Thermoplastic Starch (TPS) graft co-polymers were continuously manufactured in melt with maleic acid catalyst using a twin-screw co-rotating extruder. The graft co-polymer was completely extractable in Dichloromethane and formed transparent films on solvent casting. Regular corn-starch was maleated in a twin-screw extruder using maleic anhydride or maleic acid, glycerol plasticizer and optional radical initiator. Confirmation of reactivity of maleic acid onto the starch backbone was confirmed by Fourier Transformed Infra Red (FTIR) Spectroscopy. (Abstract shortened by UMI.)

Balakrishnan, Sunder

330

Encapsulation by Miniemulsion Polymerization  

NASA Astrophysics Data System (ADS)

The miniemulsion technique offers the possibility for the encapsulation of different materials, ranging from liquid to solid, from organic to inorganic, and from molecularly dissolved to aggregated species into polymeric nanoparticles or nanocapsules. Using this technique, a wide variety of novel functional nanomaterials can be generated. This review focuses on the preparation of functional nanostructures by encapsulating organic or inorganic material in polymeric nanoparticles. The examples demonstrate the possibilities to protect the encapsulated material as dyes, pigments, fragrances, photo-initiators, drugs, magnetite, or even DNA, use them as marker systems (dyes, magnetite), or create nanoparticles with completely new properties.

Landfester, Katharina; Weiss, Clemens K.

331

Periorbital fat grafting.  

PubMed

Periorbital aging is a multifactorial process involving volume loss (bone and soft tissue), tissue decent, and cutaneous degenerative changes. Traditional approaches to surgery on this area of the face have been subtractive in nature, focusing on excision of skin, muscle, and fat. This has frequently led to a gaunt or hollowed postoperative appearance. Contemporary aesthetic eyelid and periorbital rejuvenation has undergone a paradigm shift from an excisionally based surgical approach to one that prioritizes volume preservation and/or augmentation. The development of fat grafting to the eyelids and periorbita has given the eyelid surgeon a viable surgical alternative to prevent postoperative volume depletion, maintain the smooth transition of the lower eyelid to the cheek, and aid in restoring the youthful appearance desired after surgery. This article will focus of periorbital fat grafting and touch upon fat preservation techniques as primary restorative procedures or as surgical adjuncts. PMID:23426752

Massry, Guy G; Azizzadeh, Babak

2013-02-01

332

Grafted megaporous materials as ion-exchangers for bioproduct adsorption.  

PubMed

Megaporous chromatographic materials were manufactured by a three-step procedure, including backbone synthesis, chemical grafting, and introduction of ion-exchange functionality. The backbone of the adsorbent cylindrical bodies was prepared by polymerization of methacrylic acid and poly(ethylene glycol) diacrylate at sub-zero temperatures. Grafting was performed employing glycidyl methacrylate and a chemical initiator, cerium ammonium nitrate. The degree of grafting was adjusted by modifying the concentration of the initiator in the reaction mixture to a range of values (23, 39, 62, 89, and 105%). Further, the pendant epoxy-groups generated by the previous step were reacted to cation- and anion-exchanging moieties utilizing known chemical routes. Infrared spectroscopy studies confirmed the incorporation of epoxy and ion-exchanger groups to the backbone material. Optimized materials were tested for chromatography applications with model proteins; the dynamic binding capacity, as recorded at 10% breakthrough and 2.0 × 10(-4) m/s superficial velocity, were 350 and 58 mg/g for the cation-exchanger and the anion-exchanger material, respectively. These results may indicate that long tentacle-type polymer brushes were formed during grafting therefore increasing the ability of the megaporous body to efficiently capture macromolecules. PMID:23401432

Bibi, Noor Shad; Fernández-Lahore, Marcelo

2013-01-01

333

Siloxane-grafted membranes  

DOEpatents

Composite cellulosic semipermeable membranes are disclosed which are the covalently bonded reaction product of an asymmetric cellulosic semipermeable membrane and a polysiloxane containing reactive functional groups. The two reactants chemically bond by ether, ester, amide or acrylate linkages to form a siloxane-grafted cellulosic membrane having superior selectivity and flux stability. Selectivity may be enhanced by wetting the surface with a swelling agent such as water.

Friesen, Dwayne T. (Bend, OR); Obligin, Alan S. (Catonville, MD)

1989-01-01

334

Free vascularized fibula grafting  

Microsoft Academic Search

Summary  Eight patients with bone tumor, nonunion of fracture and extensive bony defect were treated by using the technique of free\\u000a vascularized fibula graft. Seven cases were successful and one case failed because of infection. Convalescence was shortened\\u000a significantly. A full description of the operative procedure is presented, with a review of relevant literature and a discussion\\u000a of the historical aspects

Xian Woquan; Hong Guangxiang; Zhu Tongbo

1981-01-01

335

Plasma Polymerization on Metals  

Microsoft Academic Search

An ellipsometric technique is described for accurately measuring the film thickness of plasma-polymerized polymers on metallic substrates. The index of refraction n and absorption index Kof the plasma polymer film can also be studied by ellipsometry. Films of plasma polystyrene and polyepichlorohydrin were deposited on evaporated aluminum substrates and their thickness and optical constants determined. Plasma polystyrene films from 20

P. J. Dynes; D. H. Kaelble

1976-01-01

336

Protein specific polymeric immunomicrospheres  

NASA Technical Reports Server (NTRS)

Small, round, bio-compatible microspheres capable of covalently bonding proteins and having a uniform diameter below about 3500 A are prepared by substantially instantaneously initiating polymerization of an aqueous emulsion containing no more than 35% total monomer including an acrylic monomer substituted with a covalently bondable group such as hydroxyl, amino or carboxyl and a minor amount of a cross-linking agent.

Rembaum, Alan (Inventor); Yen, Shiao-Ping S. (Inventor); Dreyer, William J. (Inventor)

1980-01-01

337

Variable Effect during Polymerization  

ERIC Educational Resources Information Center

An experiment performing the polymerization of 3-methylthiophene(P-3MT) onto the conditions for the selective electrode to determine the catechol by using cyclic voltammetry was performed. The P-3MT formed under optimized conditions improved electrochemical reversibility, selectivity and reproducibility for the detection of the catechol.

Lunsford, S. K.

2005-01-01

338

Synthesis, Structure, and Thermal Stability of a Sulfonic Cation Exchanger Grafted to Carbonized Fiber  

Microsoft Academic Search

A new kind of sulfonic cation exchanger based on carbonized fiber modified with poly(styrene-divinylbenzene) was prepared by radiation grafting. The structural features and thermal stability of the cation exchangers prepared were studied.

Yu. G. Egiazarov; L. N. Shachenkova; V. Z. Radkevich; G. N. Lysenko; B. Kh. Cherches

2005-01-01

339

Molecular architecture requirements for polymer-grafted lignin superplasticizers.  

PubMed

Superplasticizers are a class of anionic polymer dispersants used to inhibit aggregation in hydraulic cement, lowering the yield stress of cement pastes to improve workability and reduce water requirements. The plant-derived biopolymer lignin is commonly used as a low-cost/low-performance plasticizer, but attempts to improve its effects on cement rheology through copolymerization with synthetic monomers have not led to significant improvements. Here we demonstrate that kraft lignin can form the basis for high-performance superplasticizers in hydraulic cement, but the molecular architecture must be based on a lignin core with a synthetic-polymer corona that can be produced via controlled radical polymerization. Using slump tests of ordinary Portland cement pastes, we show that polyacrylamide-grafted lignin prepared via reversible addition-fragmentation chain transfer polymerization can reduce the yield stress of cement paste to similar levels as a leading commercial polycarboxylate ether superplasticizer at concentrations ten-fold lower, although the lignin material produced via controlled radical polymerization does not appear to reduce the dynamic viscosity of cement paste as effectively as the polycarboxylate superplasticizer, despite having a similar affinity for the individual mineral components of ordinary Portland cement. In contrast, polyacrylamide copolymerized with a methacrylated kraft lignin via conventional free radical polymerization having a similar overall composition did not reduce the yield stress or the viscosity of cement pastes. While further work is required to elucidate the mechanism of this effect, these results indicate that controlling the architecture of polymer-grafted lignin can significantly enhance its performance as a superplasticizer for cement. PMID:25693832

Gupta, Chetali; Sverdlove, Madeline J; Washburn, Newell R

2015-03-18

340

Influence of the polymeric interphase design on the interfacial properties of (fiber-reinforced) composites.  

PubMed

In fiber-reinforced composites, the interphase nanostructure (i.e., the extended region between two phases in contact) has a pronounced influence on their interfacial adhesion. This work aims at establishing a link between the interphase design of PS-based polymeric fiber coatings and their influence on the micromechanical performance of epoxy-based composite materials. Thiol-ene photochemistry was utilized to introduce a polymeric gradient on silica-like surfaces following a two-step approach without additional photoinitiator. Two complementary grafting-techniques were adapted to modify glass fibers: "Grafting-onto" deposition of PB-b-PS diblock copolymers for thin-film coatings (thickness<20 nm) at low grafting density (<0.1 chains/nm2)--and "grafting-from" polymerization for brush-like PS homopolymer coatings of higher thickness (up to 225 nm) and higher density. Polymer-coated glass fibers were characterized for polymer content using thermogravimetric analysis (TGA) and their nanostructural morphologies by scanning electron microscopy (SEM). Model substrates of flat glass and silicon were studied by atomic force microscopy (AFM) and spectroscopic ellipsometry (SE). The change in interfacial shear strength (IFSS) due to fiber modification was determined by a single fiber pull-out experiment. Thick coatings (>40 nm) resulted in a 50% decrease in IFSS. Higher shear strength occurred for thinner coatings of homopolymer and for lower grafting densities of copolymer. Increased IFSS (10%) was found upon dilution of the surface chain density by mixing copolymers. We show that the interfacial shear strength can be increased by tailoring of the interphase design, even for systems with inherently poor adhesion. Perspectives of polymeric fiber coatings for tailored matrix-fiber compatibility and interfacial adhesion are discussed. PMID:23446425

Kuttner, Christian; Hanisch, Andreas; Schmalz, Holger; Eder, Michaela; Schlaad, Helmut; Burgert, Ingo; Fery, Andreas

2013-04-10

341

Radiation  

Cancer.gov

DCEG researchers carry out a broad-based research program designed to identify, understand, and quantify the risk of cancer in populations exposed to medical, occupational, or environmental radiation. They study ionizing radiation exposures (e.g., x-rays,

342

RAFT-synthesized Graft Copolymers that Enhance pH-dependent Membrane Destabilization and Protein Circulation Times  

PubMed Central

Here we describe a new graft copolymer architecture of poly(propylacrylic acid) (polyPAA) that displays potent pH-dependent, membrane-destabilizing activity and in addition is shown to enhance protein blood circulation kinetics. PolyPAA containing a single telechelic alkyne functionality was prepared via reversible addition-fragmentation chain transfer (RAFT) polymerization with an alkyne-functional chain transfer agent (CTA) and coupled to RAFT polymerized poly(azidopropyl methacrylate) (polyAPMA) through azide-alkyne [3+2] Huisgen cycloaddition. The graft copolymers become membrane destabilizing at endosomal pH values and are active at significantly lower concentrations than the linear polyPAA. A biotin terminated polyPAA graft copolymer was prepared by grafting PAA onto polyAPMA polymerized with a biotin functional RAFT CTA. The blood circulation time and biodistribution of tritium labeled avidin conjugated to the polyPAA graft copolymer was characterized along with a clinically utilized 40 kDa branched polyethylene glycol (PEG) also possessing biotin functionalization. The linear and graft polyPAA increase the area under the curve (AUC) over avidin alone by 9 and 12 times, respectively. Furthermore, polyPAA graft copolymer conjugates accumulated in tumor tissue significantly more than the linear polyPAA and the branched PEG conjugates. The collective data presented in this report indicate that the polyPAA graft copolymers exhibit robust pH-dependent, membrane-destabilizing activity, low cytotoxicity and significantly enhance blood circulation time and tumor accumulation. PMID:21699931

Crownover, Emily; Duvall, Craig L.; Convertine, Anthony; Hoffman, Allan S.; Stayton, Patrick S.

2012-01-01

343

Polymeric blends for sensor and actuation dual functionality  

NASA Technical Reports Server (NTRS)

The invention described herein supplies a new class of electroactive polymeric blend materials which offer both sensing and actuation dual functionality. The blend comprises two components, one component having a sensing capability and the other component having an actuating capability. These components should be co-processable and coexisting in a phase separated blend system. Specifically, the materials are blends of a sensing component selected from the group consisting of ferroelectric, piezoelectric, pyroelectric and photoelectric polymers and an actuating component that responds to an electric field in terms of dimensional change. Said actuating component includes, but is not limited to, electrostrictive graft elastomers, dielectric electroactive elastomers, liquid crystal electroactive elastomers and field responsive polymeric gels. The sensor functionality and actuation functionality are designed by tailoring the relative fraction of the two components. The temperature dependence of the piezoelectric response and the mechanical toughness of the dual functional blends are also tailored by the composition adjustment.

St. Clair, Terry L. (Inventor); Harrison, Joycelyn S. (Inventor); Su, Ji (Inventor); Ounaies, Zoubeida (Inventor)

2004-01-01

344

Durability of Polymeric Glazing and Absorber Materials  

SciTech Connect

The Solar Heating and Lighting Program has set the goal of reducing the cost of solar water heating systems by at least 50%. An attractive approach to such large cost reduction is to replace glass and metal parts with less-expensive, lighter-weight, more-integrated polymeric components. The key challenge with polymers is to maintain performance and assure requisite durability for extended lifetimes. The objective of this task is to quantify lifetimes through measurement of the optical and mechanical stability of candidate polymeric glazing and absorber materials. Polycarbonate sheet glazings, as proposed by two industry partners, have been tested for resistance to UV radiation with three complementary methods. Incorporation of a specific 2-mil thick UV-absorbing screening layer results in glazing lifetimes of at least 15 years; improved screens promise even longer lifetimes. Proposed absorber materials were tested for creep and embrittlement under high temperature, and appear adequate for planned ICS absorbers.

Jorgensen, G.; Terwilliger, K.; Bingham, C.; Milbourne, M.

2005-01-01

345

Coronary Artery Bypass Graft  

NSDL National Science Digital Library

This patient education program explains the benefits and risks of coronary artery bypass graft surgery for the treatment of coronary arteriosclerosis. This is a MedlinePlus Interactive Health Tutorial from the National Library of Medicine, designed and developed by the Patient Education Institute. NOTE: The tutorial requires a special Flash plug-in, version 4 or above. If you do not have Flash, you will be prompted to obtain a free download of the software before you start the tutorial. You will also need an Acrobat Reader, available as a free download, in order to view the Reference Summary

Patient Education Institute

346

Rheologie des Polymeres Charges  

NASA Astrophysics Data System (ADS)

Une etude des proprietes rheologiques en ecoulement oscillatoire et en ecoulement transitoire a ete realisee sur des suspensions de particules spheriques dans des solutions de polymere d'une part et dans des polymeres a l'etat fondu d'autre part. Une attention particuliere a ete portee sur l'influence des parametres suivants sur les proprietes en ecoulement de ces fluides complexes: nature du fluide suspendant, fraction volumique en particule, temperature. Apres analyse des resultats, de nouveaux modeles empiriques ont ete proposes afin de predire l'allure des courbes d'ecoulement de ces suspensions en cisaillement oscillatoire. Enfin, certaines analogies entre les proprietes visqueuses et viscoelastiques des suspensions dans les deux milieux mentionnes precedemment ont ete discutees.

Lepez, Olivier

347

Synthesis of perm-selective membranes by grafting acrylic acid into air-irradiated Teflon-FEP films  

NASA Astrophysics Data System (ADS)

Grafting acrylic acid into air-irradiated Teflon-FEP films was investigated. Pre-irradiation doses ranged from 0.5 to 10 kGy. Grafting occurred at 45 or 60°C. Homopolymerization inhibitors, ferrous ions or methylene blue, were added to the system. It was found that after completion of the reaction, within 40-100 min, membranes were obtained with very low electric resistivities. The influence of added inhibitors, pre-irradiation dose and grafting temperature was studied. From the results it is concluded that the initiating centers in air-irradiated Teflon-FEP are, on the one hand, peroxides of structure POOP', in which P is a polymeric radical and Pprime; a small fragment, and on the other trapped PO .2 radicals. The latter only react after losing their oxygen. In the presence of polymerization inhibitors, initiation involves a redox process which reduces the overall activation energy.

Bozzi, Annick; Chapiro, Adolphe

348

Modeling oscillatory microtubule polymerization  

NASA Astrophysics Data System (ADS)

Polymerization of microtubules is ubiquitous in biological cells and under certain conditions it becomes oscillatory in time. Here, simple reaction models are analyzed that capture such oscillations as well as the length distribution of microtubules. We assume reaction conditions that are stationary over many oscillation periods, and it is a Hopf bifurcation that leads to a persistent oscillatory microtubule polymerization in these models. Analytical expressions are derived for the threshold of the bifurcation and the oscillation frequency in terms of reaction rates, and typical trends of their parameter dependence are presented. Both, a catastrophe rate that depends on the density of guanosine triphosphate liganded tubulin dimers and a delay reaction, such as the depolymerization of shrinking microtubules or the decay of oligomers, support oscillations. For a tubulin dimer concentration below the threshold, oscillatory microtubule polymerization occurs transiently on the route to a stationary state, as shown by numerical solutions of the model equations. Close to threshold, a so-called amplitude equation is derived and it is shown that the bifurcation to microtubule oscillations is supercritical.

Hammele, Martin; Zimmermann, Walter

2003-02-01

349

Developments in polymerization lamps.  

PubMed

Polymerization shrinkage of composite resins and the consequent stress generated at the composite-tooth interface continue to pose a serious clinical challenge. The development of high-intensity halogen lamps and the advent of curing units providing higher energy performance, such as laser lamps, plasma arc units, and, most recently, light-emitting diode (LED) curing units, have revolutionized polymerization lamp use and brought major changes in light-application techniques. A comprehensive review of the literature yielded the following conclusions: (1) the most reliable curing unit for any type of composite resin is the high-density halogen lamp, fitted with a programming device to enable both pulse-delay and soft-start techniques; (2) if any other type of curing unit is used, information must be available on the compatibility of the unit with the composite materials to be used; (3) polymerization lamp manufacturers need to focus on the ongoing development of LED technology; (4) further research is required to identify the most reliable light-application techniques. PMID:18560645

Jiménez-Planas, Amparo; Martín, Juan; Abalos, Camilo; Llamas, Rafael

2008-02-01

350

Polyether/Polyester Graft Copolymers  

NASA Technical Reports Server (NTRS)

Higher solvent resistance achieved along with lower melting temperature. New technique provides method of preparing copolymers with polypivalolactone segments grafted onto poly (2,6-dimethyl-phenylene oxide) backbone. Process makes strong materials with improved solvent resistance and crystalline, thermally-reversible crosslinks. Resulting graft copolymers easier to fabricate into useful articles, including thin films, sheets, fibers, foams, laminates, and moldings.

Bell, Vernon L., Jr.; Wakelyn, N.; Stoakley, D. M.; Proctor, K. M.

1986-01-01

351

Grafting effects on vegetable quality  

Technology Transfer Automated Retrieval System (TEKTRAN)

Vegetable grafting began in the 1920s to control soil-borne disease. It is now a common practice in Asia, parts of Europe, and the Middle East. In Japan and Korea most of the cucurbits and tomatoes (Lycopersicon esculentum Mill.) grown are grafted. This practice is rare in the U.S. and there have...

352

ACL Reconstruction: Choosing the Graft  

PubMed Central

Summary Rupture of the anterior cruciate ligament is one of the most common ligament injuries in sports traumatology. The need for surgical anterior cruciate ligament reconstruction is justified by its anatomical characteristics. Key considerations when choosing a graft include the potential for bone integration and the risk of failure. Bone sclerosis around the tunnel affects the integration of the graft. For this reason, one aspect upon which orthopedic surgeons should focus is the biology of the bone-graft interface. Although the BPTB graft is still used, hamstrings and synthetic grafts have become increasingly widespread and popular over the years. An allograft certainly requires more long-term follow-up to validate its use in response to functional, clinical and biological requirements. PMID:25606507

Cerulli, Giuliano; Placella, Giacomo; Sebastiani, Enrico; Tei, Matteo Maria; Speziali, Andrea; Manfreda, Francesco

2013-01-01

353

High energy radiation grafting of fluoropolymers  

Microsoft Academic Search

Fluoropolymers are known as chemically inert materials with good high temperature resistance, so they are often the materials of choice for harsh chemical environments. These properties arise because the carbon–fluorine bond is the strongest of all bonds between other elements and carbon, and, because of their large size, fluorine atoms can protect the carbon backbone of polymers such as poly(tetrafluoroethylene),

Tim R Dargaville; Graeme A George; David J. T Hill; Andrew K Whittaker

2003-01-01

354

Surface-Initiated Atom Transfer Radical Polymerization Si-Atrp of Acrylamide from Poly(vinyl Chloride) Film and its Sorption Property Toward Mercury Ion  

NASA Astrophysics Data System (ADS)

The polyacrylamide surface grafted poly(vinyl chloride) (PAM-PVC) film was successfully prepared via a facile copper-mediated surface-initiated atom transfer radical polymerization (SI-ATRP) of acrylamide (AM) from the surfaces of the PVC thin film with their surface labile chlorines as initiation sites. Graft reaction was first-order kinetic with respect to the polymerizing time in the low monomer conversion stage, this being typical for ATRP. A percentage of grafting (PG) of 32.1% was achieved in 6 h, calculated from the elemental analysis results. The surface morphology of the product was characterized with scanning electron microscopy (SEM). The sorption property of the grafted film toward Hg(II) ion was also preliminarily investigated.

Liu, Peng

355

Performance of vanadium redox flow battery with a novel amphoteric ion exchange membrane synthesized by two-step grafting method  

Microsoft Academic Search

A novel ETFE-based amphoteric ion exchange membrane (AIEM) was prepared through a two-step radiation-induced grafting technique. ETFE film was first grafted with styrene (St) (denoted as ETFE-g-PS), followed with a sulfonation treatment to obtain a cation exchange membrane (ETFE-g-PSSA). The ETFE-g-PSSA membrane was subsequently grafted with dimethylaminoethyl methacrylate (DMAEMA) and then protonated, resulting in an AIEM with both anionic and

Jingyi Qiu; Maolin Zhai; Jinhua Chen; Yu Wang; Jing Peng; Ling Xu; Jiuqiang Li; Genshuan Wei

2009-01-01

356

Preparation of poly( p-styrenesulfonic acid) grafted multi-walled carbon nanotubes and their application as a solid-acid catalyst  

Microsoft Academic Search

Poly(p-styenesulfonate acid)-grafted multi-walled carbon nanotubes (PSSA-g-MWCNTs) were prepared by in situ polymerization of sodium p-styrenesulfonate in the presence of MWCNTs, followed by refluxing with concentrated hydrochloric acid. In this reaction system, sodium p-styrenesulfonate served not only as the reaction monomer but also as an amphiphilic dispersant to disperse pristine MWCNTs in water, which is critical for the grafting PSSA onto

Xiao-Hong Zhang; Qian-Qian Tang; Dong Yang; Wei-Ming Hua; Ying-Hong Yue; Bei-Di Wang; Xiao-Huan Zhang; Jian-Hua Hu

2011-01-01

357

Chitosan\\/oligo L-lactide graft copolymers: Effect of hydrophobic side chains on the physico-chemical properties and biodegradability  

Microsoft Academic Search

Graft copolymerization of L-lactide (LLA) onto chitosan (CS) was carried out by ring opening polymerisation using Ti(OBu)4 as catalyst in DMSO at 90°C in nitrogen atmosphere to obtain chitosan\\/oligo L-lactide graft copolymers (CL). The ring opening polymerisation of L-lactide using a covalent initiator would significantly reduce the risk of racemization even at high temperatures in comparison to other polymerization methods.

Gisha Elizabeth Luckachan; C. K. S. Pillai

2006-01-01

358

Polymeric salt bridges for conducting electric current in microfluidic devices  

DOEpatents

A "cast-in-place" monolithic microporous polymer salt bridge for conducting electrical current in microfluidic devices, and methods for manufacture thereof is disclosed. Polymeric salt bridges are formed in place in capillaries or microchannels. Formulations are prepared with monomer, suitable cross-linkers, solvent, and a thermal or radiation responsive initiator. The formulation is placed in a desired location and then suitable radiation such as UV light is used to polymerize the salt bridge within a desired structural location. Embodiments are provided wherein the polymeric salt bridges have sufficient porosity to allow ionic migration without bulk flow of solvents therethrough. The salt bridges form barriers that seal against fluid pressures in excess of 5000 pounds per square inch. The salt bridges can be formulated for carriage of suitable amperage at a desired voltage, and thus microfluidic devices using such salt bridges can be specifically constructed to meet selected analytical requirements.

Shepodd, Timothy J. (Livermore, CA); Tichenor, Mark S. (San Diego, CA); Artau, Alexander (Humacao, PR)

2009-11-17

359

Polymerization Evaluation by Spectrophotometric Measurements.  

ERIC Educational Resources Information Center

Discusses polymerization evaluation by spectrophotometric measurements by considering: (1) association degrees and molar absorptivities; (2) association degrees and equilibrium constants; and (3) absorbance and equilibrium constants. (JN)

Dunach, Jaume

1985-01-01

360

POLYMERIZATION OF RIBOMONONUCLEOTIDES BY $gamma$RADIATION  

Microsoft Academic Search

After gamma irradiation (0.9- 18.0 x 10⁴ r) of ; ribomononucleotides in aqueous solution a decrease in absorbancy at 260 m mu of ; at least two different components was observed. The decrease is an exponential ; function of the dose. Alkaline and enzymic hydrolysis with RNAase or ; phosphodiesterase of the irradiated samples produced an hyperchromic effect. ; Paper

G. Contreras; R. Espejo; E. Mery; A. Ohlbaum; J. Toha

1962-01-01

361

Surface grafting of microfibrillated cellulose with poly( ?-caprolactone) – Synthesis and characterization  

Microsoft Academic Search

In cellulose nanocomposites, the surface of the nanocellulosic phase is critical with respect to nanocellulose dispersion, network formation and nanocomposite properties. Microfibrillated cellulose (MFC) has been grafted with poly(?-caprolactone) (PCL), via ring-opening polymerization (ROP). This changes the surface characteristics of MFC and makes it possible to obtain a stable dispersion of MFC in a nonpolar solvent; it also improves MFC’s

Hanna Lönnberg; Linda Fogelström; Lars Berglund; Eva Malmström; Anders Hult

2008-01-01

362

Surface grafting of microfibrillated cellulose with poly(e-caprolactone) - Synthesis and characterization  

Microsoft Academic Search

a b s t r a c t In cellulose nanocomposites, the surface of the nanocellulosic phase is critical with respect to nanocellulose dispersion, network formation and nanocomposite properties. Microfibr- illated cellulose (MFC) has been grafted with poly(e-caprolactone) (PCL), via ring-opening polymerization (ROP). This changes the surface characteristics of MFC and makes it possi- ble to obtain a stable dispersion

Hanna Lönnberg; Azizi Samir; Lars Berglund; Eva Malmström; Anders Hult

2008-01-01

363

Grafting of Polystyrene-b-Poly(2-hydroxyethyl methacrylate) onto Carbon Fiber  

Microsoft Academic Search

Carbon fiber (CF) was subjected to oxidation and acyl chlorination, resulting in CF functionalized with acyl chloride (CF-COCl). The block copolymer polystyrene-b-poly (2-hydroxyethyl methacrylate) (PSt-b-PHEMA) was synthesized by atom-transfer radical polymerization (ATRP). According to the reaction between hydroxyl groups of block copolymer and acyl chloride groups on CF, the block copolymer was successfully grafted onto the surface of CF. Fourier-transform

Jingqiang Hou; Xiaodong Zhou

2008-01-01

364

Grafted CMC and Sodium Alginate: A Comparison in their Flocculation Performance  

Microsoft Academic Search

Synthesis of Carboxymethylcellulose-g-Polyacrylamide was carried out in ceric ion induced redox polymerization technique at 29 ą 1°C. The graft copolymer was characterised by intrinsic viscosity measurement and IR spectroscopy. The flocculation performance of CMC-g-PAM and sodium alginate-g-PAM was tested in both 1 wt% coking and non-coking coal fine suspensions. The flocculation performance of CMC-g-PAM is better than that of SAG-g-PAM

Tridib Tripathy; N. C. Karmakar; R. P. Singh

2000-01-01

365

Hydrolyzed polyacrylamide grafted maize starch based microbeads: application in pH responsive drug delivery.  

PubMed

The present study details the synthesis, characterization and pharmaceutical application of hydrolysed polyacrylamide grafted maize starch (HPam-g-MS) as promising polymeric material for the development of pH responsive microbeads. Different grades of graft copolymer were synthesized by changing the net microwave irradiation time, while keeping all other factors constant. Acute oral toxicity study performed in rodents ensured the bio-safety of graft copolymer for clinical application. Various batches of aceclofenac loaded microbeads were prepared by ionic gelation method using synthesized graft copolymers and evaluated for formulation parameters. FTIR spectroscopy confirmed the chemical compatibility between drug and graft copolymer. Results of in vitro release study (USP type-II) carried out in two different pH media (pH 1.2 acid buffer and pH 7.4 phosphate buffer) showed that release rate of drug from developed microbeads was a function of both: (a) surrounding pH and (b) the matrix composition. The drug release was relatively higher at alkaline pH as compared to acidic pH and this feature is desirable from viewpoint of site specific drug delivery. A direct correlation was observed between percentage grafting and microbeads performance and it presents a scope for further research on application and optimization of HPam-g-MS based microbeads as drug delivery carriers. PMID:24971555

Setty, C Mallikarjuna; Deshmukh, Anand S; Badiger, Aravind M

2014-09-01

366

Biotribological properties of UHMWPE grafted with AA under lubrication as artificial joint.  

PubMed

Osteolysis caused by wear particles from polyethylene in the artificial hip joints is a serious issue. In order to endow the low friction and wear of the bearing surface of ultra-high molecular weight polyethylene (UHMWPE) artificial joint for a longer term, hydrophilic acrylic acid (AA) was grafted on UHMWPE powders with the method of ultraviolet irradiation and then the modified powders were hot pressed. The tribological properties of modified UHMWPE sliding against CoCrMo metallic plate on reciprocating tribometer under calf serum, saline and distilled water lubrication during a long-term friction were investigated. The measurement of Fourier-transform infrared spectroscopy indicates that AA is successfully grafted on the surface of UHMWPE powders by photo-induced graft polymerization. Contact angles of UHMWPE are decreased from 83° to 35° by grafting and the surface wettability is effectively improved. The tensile strength of modified sample decreases. The friction coefficient and wear rate of UHMWPE-g-PAA under calf serum, saline and distilled water lubrication are lower than that of untreated UHMWPE. With the increase of grafting ratio, the wear rate of UHMWPE-g-PAA decreases firstly and then increases. The modified UHMWPE with grafting ratio of 3.5 % has the lowest wear rate, which is just quarter of the untreated UHMWPE. The hydrated PAA polymer brushes enclosed in the UHMWPE bulk material provide continuous lubrication during long term sliding. PMID:23793532

Deng, Yaling; Xiong, Dangsheng; Wang, Kun

2013-09-01

367

Robot-Assisted Antegrade In-Situ Fenestrated Stent Grafting  

SciTech Connect

To determine the technical feasibility of a novel approach of in-situ fenestration of aortic stent grafts by using a remotely controlled robotic steerable catheter system in the porcine model. A 65-kg pig underwent robot-assisted bilateral antegrade in-situ renal fenestration of an abdominal aortic stent graft with subsequent successful deployment of a bare metal stent into the right renal artery. A 16-mm iliac extension covered stent served as the porcine aortic endograft. Under fluoroscopic guidance, the graft was punctured with a 20-G customized diathermy needle that was introduced and kept in place by the robotic arm. The needle was exchanged for a 4 x 20 mm cutting balloon before successful deployment of the renal stent. Robot-assisted antegrade in-situ fenestration is technically feasible in a large mammalian model. The robotic system enables precise manipulation, stable positioning, and minimum instrumentation of the aorta and its branches while minimizing radiation exposure.

Riga, Celia V., E-mail: c.riga@imperial.ac.uk; Bicknell, Colin D. [Imperial College Healthcare, St Mary's Hospital, Regional Vascular Unit (United Kingdom); Wallace, Daniel [Hansen Medical (United States); Hamady, Mohamad; Cheshire, Nicholas [Imperial College Healthcare, St Mary's Hospital, Regional Vascular Unit (United Kingdom)

2009-05-15

368

Graft healing in anterior cruciate ligament reconstruction  

Microsoft Academic Search

Successful anterior cruciate ligament reconstruction with a tendon graft necessitates solid healing of the tendon graft in the bone tunnel. Improvement of graft healing to bone is crucial for facilitating an early and aggressive rehabilitation and ensuring rapid return to pre-injury levels activity. Tendon graft healing in a bone tunnel requires bone ingrowth into the tendon. Indirect Sharpey fiber formation

Chih-Hwa Chen

2009-01-01

369

Graft healing in anterior cruciate ligament reconstruction.  

PubMed

Graft healing within the bone tunnel after anterior cruciate ligament (ACL) reconstruction is still a complex, poorly understood biological process that is influenced by multiple surgical and postoperative variables. However, remarkable advances in knowledge of this process have been made based primarly on animal models. According to the findings of this review, some surgical and postoperative variables are known to directly affect time-course and quality of graft-tunnel healing. The type of graft, graft motion, and fixation methods have shown to directly affect time-course and quality of graft-tunnel healing. Therefore, the application of early and aggressive rehabilitation protocols should be cautious when using soft-tissue graft, allografts, and direct or aperture type of fixation for ACL reconstruction. With regard to graft placement, several cadaveric models showed biomechanical advantages of a more anatomical graft location; however, there are no studies that explore the relationship between graft placement and healing process. The precise effect of graft tensioning, graft/tunnel diameter disparity, and graft length within the bone tunnel in the graft healing process remains unclear and requires more research. To enhance graft-tunnel healing, tissue-engineering approaches, including the use of growth factors, mesenchymal stem cells, and periosteum graft augmentation, have been tested on animal models. These have shown promising results in terms of enhancement of bone-graft healing rate. PMID:18633596

Ekdahl, Max; Wang, James H-C; Ronga, Mario; Fu, Freddie H

2008-10-01

370

Living olefin polymerization processes  

DOEpatents

Processes for the living polymerization of olefin monomers with terminal carbon-carbon double bonds are disclosed. The processes employ initiators that include a metal atom and a ligand having two group 15 atoms and a group 16 atom or three group 15 atoms. The ligand is bonded to the metal atom through two anionic or covalent bonds and a dative bond. The initiators are particularly stable under reaction conditions in the absence of olefin monomer. The processes provide polymers having low polydispersities, especially block copolymers having low polydispersities. It is an additional advantage of these processes that, during block copolymer synthesis, a relatively small amount of homopolymer is formed.

Schrock, Richard R.; Baumann, Robert

2003-08-26

371

Living olefin polymerization processes  

DOEpatents

Processes for the living polymerization of olefin monomers with terminal carbon-carbon double bonds are disclosed. The processes employ initiators that include a metal atom and a ligand having two group 15 atoms and a group 16 atom or three group 15 atoms. The ligand is bonded to the metal atom through two anionic or covalent bonds and a dative bond. The initiators are particularly stable under reaction conditions in the absence of olefin monomer. The processes provide polymers having low polydispersities, especially block copolymers having low polydispersities. It is an additional advantage of these processes that, during block copolymer synthesis, a relatively small amount of homopolymer is formed.

Schrock, Richard R.; Bauman, Robert

2006-11-14

372

Living olefin polymerization processes  

DOEpatents

Processes for the living polymerization of olefin monomers with terminal carbon-carbon double bonds are disclosed. The processes employ initiators that include a metal atom and a ligand having two group 15 atoms and a group 16 atom or three group 15 atoms. The ligand is bonded to the metal atom through two anionic or covalent bonds and a dative bond. The initiators are particularly stable under reaction conditions in the absence of olefin monomer. The processes provide polymers having low polydispersities, especially block copolymers having low polydispersities. It is an additional advantage of these processes that, during block copolymer synthesis, a relatively small amount of homopolymer is formed.

Schrock, R.R.; Baumann, R.

1999-03-30

373

Living olefin polymerization processes  

DOEpatents

Processes for the living polymerization of olefin monomers with terminal carbon-carbon double bonds are disclosed. The processes employ initiators that include a metal atom and a ligand having two group 15 atoms and a group 16 atom or three group 15 atoms. The ligand is bonded to the metal atom through two anionic or covalent bonds and a dative bond. The initiators are particularly stable under reaction conditions in the absence of olefin monomer. The processes provide polymers having low polydispersities, especially block copolymers having low polydispersities. It is an additional advantage of these processes that, during block copolymer synthesis, a relatively small amount of homopolymer is formed.

Schrock, Richard R. (Winchester, MA); Baumann, Robert (Cambridge, MA)

1999-01-01

374

Bimorphic polymeric photomechanical actuator  

NASA Technical Reports Server (NTRS)

A bimorphic polymeric photomechanical actuator, in one embodiment using polyvinylidene fluoride (PVDF) as a photosensitive body, transmitting light over fiber optic cables, and controlling the shape and pulse duration of the light pulse to control movement of the actuator. Multiple light beams are utilized to generate different ranges of motion for the actuator from a single photomechanical body and alternative designs use multiple light beams and multiple photomechanical bodies to provide controlled movement. Actuator movement using one or more ranges of motion is utilized to control motion to position an actuating element in three dimensional space.

Sarkisov, Sergey S. (Inventor); Curley, Michael J. (Inventor); Adamovsky, Grigory (Inventor); Sarkisov, Jr., Sergey S. (Inventor); Fields, Aisha B. (Inventor)

2006-01-01

375

Space environmental effects on polymeric materials  

NASA Technical Reports Server (NTRS)

Polymer-matrix composites have considerable potential for use in the construction of orbiting structures such as the space station and space antennas because of their light weight, high strength, and low thermal expansion. However, they can suffer surface erosion by interaction with atomic oxygen in low-Earth orbit and degradation and/or embrittlement by electrons and ultraviolet radiation especially in geosynchronous orbit. Thus, a study of the effect of these environmental hazards on polymeric materials is an important step in the assessment of such materials for future use in space.

Kiefer, Richard L.; Orwoll, Robert A.

1988-01-01

376

Unusual costochondral bone graft complication.  

PubMed

In hemifacial microsomia, patients with severely hypoplastic mandibles (Pruzansky type III) require replacement of the ramus and condyle unit. Common complications of this procedure include graft fracture and overgrowth of the graft. An uncommon case of osteolysis of the costochondral graft with osteitis of the middle cranial fossa is reported herein. To our knowledge, no such case has been reported in the literature previously. The aim of this report is to present the only known case and to discuss the contributing factors. PMID:23972557

Tabchouri, Nathalie; Kadlub, Natacha; Diner, Patrick A; Picard, Arnaud

2013-11-01

377

Novel macromonomer as a reactive stabilizer in the dispersion polymerization of methylmethacrylate  

Microsoft Academic Search

We have synthesized a novel macromonomer of vinyl-terminated bifunctional polyurethane having a molecular weight of 37,000\\u000a g\\/mol and successfully applied it to the dispersion polymerization of methylmethacrylate (MMA). We verified the presence of\\u000a the vinyl terminal group and the macromonomer grafted onto the poly(ethylene glycol) (PEG) block in the PMMA particles by\\u000a using1H and13C NMR spectroscopies. Monodisperse PMMA microspheres that

Hyejun Jung; Kangseok Lee; Sang Eun Shim; Sunhye Yang; Jung Min Lee; Huije Lee; Soonja Choe

2004-01-01

378

Dispersion polymerization of methyl methacrylate with a novel bifunctional polyurethane macromonomer as a reactive stabilizer  

Microsoft Academic Search

A novel macromonomer of vinyl-terminated bifunctional polyurethane was synthesized and applied to the dispersion polymerization of MMA in ethanol. The existence of the vinyl terminal groups and the grafted macromonomer with PMMA was verified using 1H NMR and 13C NMR. The stable and monodisperse PMMA microspheres having a weight-average diameter of 5.09 ?m and a good uniformity of 1.01 were

Sang Eun Shim; Hyejun Jung; Kangseok Lee; Jung Min Lee; Soonja Choe

2004-01-01

379

Modification and characterization of prepared polysulfone ultrafi ltration membranes via photografted polymerization: Effect of different additives  

Microsoft Academic Search

The modified ultrafi ltration (UF) membranes were prepared by graft polymerization of acrylic acid (AA) that is a hydrophilic monomer onto the surface of ultrafi ltration membranes. Primary UF membranes were formed by wet phase inversion method by using polysulfone (PSf)\\/ N-methylene-2-pyrrolidone (NMP)\\/ poly (ethylene glycol) (PEG) casting solution and water coagulant. PEG acts as a pore-former that in this

M. Amini; M. Homayoonfal; M. Arami; A. Akbari

2009-01-01

380

Grafting of Chitosan and Chitosantrimethoxylsilylpropyl Methacrylate on Single Walled Carbon Nanotubes-Synthesis and Characterization  

PubMed Central

Acid functionalized single walled carbon nanotubes (CNTs) were grafted to chitosan by first reacting the oxidized CNTs with thionyl chloride to form acyl-chlorinated CNTs. This product was subsequently dispersed in chitosan and covalently grafted to form CNT-chitosan. CNT-chitosan was further grafted onto 3-trimethoxysilylpropyl methacrylate by free radical polymerization conditions, to yield CNT-g-chitosan-g-3-trimethoxysilylpropyl methacrylate (TMSPM), hereafter referred to as CNT-chitosan-3-TMSPM. These composites were characterized by Fourier Transform Infrared Resonance Spectroscopy (FTIR), carbon-13 nuclear magnetic resonance (13C NMR), Thermogravimetric Analysis (TGA), scanning electron microscopy (SEM) and transmission electron microscopy (TEM). The composite showed improved thermal stability and could be of great potential use in bone tissue engineering. PMID:21765959

Carson, Laura; Kelly-Brown, Cordella; Stewart, Melisa; Oki, Aderemi; Regisford, Gloria; Stone, Julia; Traisawatwong, Pasakorn; Durand-Rougely, Clarissa; Luo, Zhiping

2011-01-01

381

Binary mixed homopolymer brushes grafted on nanorod particles: A self-consistent field theory study  

NASA Astrophysics Data System (ADS)

We employ the self-consistent field theory to study phase structures of brush-rod systems composed of two chemically distinct linear homopolymers. The polymer chains are uniformly grafted on the surface of a nanorod particle of finite length and comparable radius to the polymer radius of gyration. A "masking" technique treating the cylindrical boundary is introduced to solve the modified diffusion equations with an efficient and high-order accurate pseudospectral method involving fast Fourier transform on an orthorhombic cell. A rich variety of structures for the phase separated brushes is predicted. Phase diagrams involving a series of system parameters, such as the aspect ratio of the nanorod, the grafting density, and the chain length are constructed. The results indicate that the phase structure of the mixed brush-rod system can be tailored by varying the grafted chain length and/or the aspect ratio of the rod to benefit the fabrication of polymeric nanocomposites.

Ma, Xin; Yang, Yingzi; Zhu, Lei; Zhao, Bin; Tang, Ping; Qiu, Feng

2013-12-01

382

Organometallic Polymeric Conductors  

NASA Technical Reports Server (NTRS)

For aerospace applications, the use of polymers can result in tremendous weight savings over metals. Suitable polymeric materials for some applications like EMI shielding, spacecraft grounding, and charge dissipation must combine high electrical conductivity with long-term environmental stability, good processability, and good mechanical properties. Recently, other investigators have reported hybrid films made from an electrically conductive polymer combined with insulating polymers. In all of these instances, the films were prepared by infiltrating an insulating polymer with a precursor for a conductive polymer (either polypyrrole or polythiophene), and oxidatively polymerizing the precursor in situ. The resulting composite films have good electrical conductivity, while overcoming the brittleness inherent in most conductive polymers. The highest conductivities reported (approximately 4/Scm) were achieved with polythiophene in a polystyrene host polymer. The best films using a polyamide as base polymer were four orders of magnitude less conductive than the polystyrene films. The authors suggested that this was because polyimides were unable to swell sufficiently for infiltration of monomer as in the polystyrene. It was not clear, however, if the different conductivities obtained were merely the result of differing oxidation conditions. Oxidation time, temperature and oxidant concentration varied widely among the studies.

1997-01-01

383

High-transparency polymer nanocomposites enabled by polymer-graft modification of particle fillers.  

PubMed

The role of polymeric ligands on the optical transparency of polymer-matrix composites is analyzed by evaluating the effect of surface modification on the scattering cross-section of particle fillers in uniform particle dispersions. For the particular case of poly(styrene-r-acrylonitrile)-grafted silica particles embedded in poly(methyl methacrylate), it is shown that the tethering of polymeric chains with appropriate optical properties (such as to match the effective refractive index of the brush particle to the embedding matrix) facilitates the reduction of the particle scattering cross-section by several orders of magnitude as compared to pristine particle analogues. The conditions for minimizing the scattering cross-section of particle fillers by polymer-graft modification are established on the basis of effective medium as well as core-shell Mie theory and validated against experimental data on uniform liquid and solid particle dispersions. Effective medium theory is demonstrated to provide robust estimates of the "optimum polymer-graft composition" to minimize the scattering cross-section of particle fillers even in the limit of large particle dimensions (comparable to the wavelength of light). The application of polymer-graft modification to the design of large (500 nm diameter) silica particle composites with reduced scattering cross-section is demonstrated. PMID:25398014

Dang, Alei; Ojha, Satyajeet; Hui, Chin Ming; Mahoney, Clare; Matyjaszewski, Krzysztof; Bockstaller, Michael R

2014-12-01

384

Coating of plasma polymerized film  

NASA Technical Reports Server (NTRS)

Plasma polymerized thin film coating and the use of other coatings is suggested for passivation film, thin film used for conducting light, and solid body lubrication film of dielectrics of ultra insulators for electrical conduction, electron accessories, etc. The special features of flow discharge development and the polymerized film growth mechanism are discussed.

Morita, S.; Ishibashi, S.

1980-01-01

385

Polymeric coatings using electronic excitation  

NASA Technical Reports Server (NTRS)

Process has been developed for glow discharge polymerization which is accomplished in inert atmosphere by using vacuum chamber. Polymeric coating, in this type of environment, produces high molecular weight coating polymers that have good stability and are resistant to abrasions and solvents.

Lee, S. M.

1972-01-01

386

Polymerization topochemistry of cellulose nanocrystals: a function of surface dehydration control.  

PubMed

The activation (dehydration) of cellulose nanocrystals (CNCs) toward surface "brush" polymerization is accomplished either by freeze drying or solvent exchange. However, the question of which one of these protocols to choose over the other is generally open-ended. The current study attempts to shed light on this question by installing a standard polymer, polycaprolactone (PCL), onto the surface of both freeze-dried and solvent-exchanged CNCs by ring-opening polymerization (ROP) and examining the differences in polymerization and final product properties. The work is the first to demonstrate that the efficiency of surface polymerization and final product properties are in fact influenced by the protocols. The differences between the two sample PCL-grafted CNCs were investigated by X-ray photoelectron spectroscopy (XPS), elemental analysis, gel permeation chromatography (GPC), and contact-angle measurements. The freeze-dried samples had a significantly reduced PCL surface density. The crystallinity of the solvent-exchanged PCL-grafted CNCs (SECNC-g-PCL), however, was lower than that of either pure CNCs or freeze-dried PCL-grafted CNCs (FDCNC-g-PCL). It was determined that solvent exchange sufficiently modified the CNC surface to provide enhanced reactivity, an effect that was not as apparent for FDCNC-g-PCL. The solvent-exchanged CNCs tended to have more porous, nanotextured surfaces that were tended to be more responsive toward brush polymerization. In addition to the physical dissimilarities in surface morphology and surface accessibility contributing to topochemical differences between the two species, it was also found that the dispersibility, aggregation, and thermal stability were different. PMID:25387043

Tian, Chen; Fu, Shiyu; Habibi, Youssef; Lucia, Lucian A

2014-12-01

387

Bone Grafts (Periodontal Regenerative Surgery)  

MedlinePLUS

... include bits of: Your own bone Cadaver bone Cow bone Synthetic glasses Your own bone is best. ... bony defect. Barriers are made from human skin, cow skin or synthetic materials. After the graft is ...

388

Brush/gold nanoparticle hybrids: effect of grafting density on the particle uptake and distribution within weak polyelectrolyte brushes.  

PubMed

The effect of the brush grafting density on the loading of 13 nm gold nanoparticles (AuNPs) into stimuli-responsive poly(N,N-(dimethylamino ethyl) methacrylate) (PDMAEMA) brushes anchored to flat impenetrable substrates is reported. Atom-transfer radical polymerization (ATRP) is used to grow polymer brushes via a "grafting from" approach from a 2-bromo-2-methyl-N-(3-(triethoxysilyl) propyl) propanamide (BTPAm)-covered silicon substrate. The grafting density is varied by using mixtures of initiator and a "dummy" molecule that is not able to initiate polymerization. A systematic study is carried out by varying the brush grafting density while keeping all of the other parameters constant. X-ray reflectivity is a suitable tool for investigating the spatial structure of the hybrid, and it is combined with scanning electron microscopy and UV/vis spectroscopy to study the particle loading and interpenetration of the particles within the polymer brush matrix. The particle uptake increases with decreasing grafting density and is highest for an intermediate grafting density because more space between the polymer chains is available. For very low grafting densities of PDMAEMA brushes, the particle uptake decreases because of a lack of the polymer matrix for the attachment of particles. The structure of the surface-grafted polymer chains changes after particle attachment. More water is incorporated into the brush matrix after particle immobilization, which leads to a swelling of the polymer chains in the hybrid material. Water can be removed from the brush by decreasing the relative humidity, which leads to brush shrinking and forces the AuNPs to get closer to each other. PMID:25275215

Christau, Stephanie; Möller, Tim; Yenice, Zuleyha; Genzer, Jan; von Klitzing, Regine

2014-11-01

389

Modification of natural and artificial polymer colloids by "topology-controlled" emulsion polymerization.  

PubMed

A diffuse layer of water-soluble polymer chemically grafted to the surface of a hydrophobic polymer colloid has been created by the second-stage polymerization of dimethylaminoethyl methacrylate (DMAEMA) onto the biomacromolecule polyisoprene in natural rubber latex and also onto synthetic polybutadiene and polystyrene latexes. To control the locus of radical formation, the process was initiated by a redox couple wherein one component (e.g., cumene hydroperoxide) is hydrophobic and the other (e.g., tetraethylenepentamine) is hydrophilic. The modified latexes displayed a dramatic increase in colloidal stability at low pH which is attributed to grafted hydrophilic polymer acting as an electrosteric stabilizer; the effect is particularly remarkable in natural rubber latex, which usually has poor colloidal stability for pH less, similar 8. (13)C NMR was performed to verify the existence of the grafted copolymer and to quantify yield. The mechanism by which such a novel morphology can be generated is postulated to be via a process of radical formation at the particle surface followed by the subsequent grafting to the hydrophobic polymer backbone and polymerization of hydrophilic monomer in the aqueous phase. This technique is potentially useful for creating novel materials from natural rubber latex. PMID:11749215

Lamb, D J; Anstey, J F; Fellows, C M; Monteiro, M J; Gilbert, R G

2001-01-01

390

Poly(vinylidene fluoride-co-hexafluoropropylene)-graft-poly(dopamine methacrylamide) copolymers: A nonlinear dielectric material for high energy density storage  

NASA Astrophysics Data System (ADS)

A nonlinear dielectric poly(vinylidene fluoride-co-hexafluoropropylene)-graft-poly(dopamine methacrylamide) [P(VDF-HFP)-g-PDMA] graft copolymer with ultra-high energy density of 33 J/cm3 was obtained by thermally initiated radical graft polymerization. It was observed that the dielectric constant of the graft copolymer films was 63% higher than that of P(VDF-HFP), with a large dielectric breakdown strength (>850 MV/m). Theoretical analyses and experimental measurements showed that the significant improvement in the electric polarization was attributed to the introduction of the highly polarizable hydroxyl groups in the PDMA side chains, and the large breakdown strength arose from the strong adhesion bonding of the catechol-containing graft copolymer to the metal electrode.

Rahimabady, Mojtaba; Qun Xu, Li; Arabnejad, Saeid; Yao, Kui; Lu, Li; Shim, Victor P. W.; Gee Neoh, Koon; Kang, En-Tang

2013-12-01

391

Interventions in Infrainguinal Bypass Grafts  

SciTech Connect

The interventional radiologist plays an important role in the detection and prevention of infrainguinal bypass failure. Early detection and evaluation of flow-limiting lesions effectively preserve graft (venous bypass and polyester or expanded polytetrafluoroethylene bypass) patency by identifying stenoses before occlusion occurs. Delay in treatment of the at-risk graft may result in graft failure and a reduced chance of successful revascularization. For this reason, surveillance protocols form an important part of follow-up after infrainguinal bypass surgery. As well as having an understanding of the application of imaging techniques including ultrasound, MR angiography, CT angiography and digital subtraction angiography, the interventional radiologist should have detailed knowledge of the minimally invasive therapeutic options. Percutaneous transluminal angioplasty (PTA), or alternatively cutting balloon angioplasty, is the interventional treatment of choice in prevention of graft failure and occlusion. Further alternatives include metallic stent placement, fibrinolysis, and mechanical thrombectomy. Primary assisted patency rates following PTA can be up to 65% at 5 years. When the endovascular approach is unsuccessful, these therapeutic options are complemented by surgical procedures including vein patch revision, jump grafting, or placement of a new graft.

Mueller-Huelsbeck, S., E-mail: muehue@rad.uni-kiel.de; Order, B.-M.; Jahnke, T. [University Hospital Schleswig-Holstein - Campus Kiel, Department of Radiology (Germany)

2006-02-15

392

[Articular reconstructions by a costochondral grafting (or osteochondral costal grafting)].  

PubMed

We describe a novel technique of costochondral autografting for the treatment of trapeziometacarpal arthritis, radioscaphoid osteoarthritis, malunion of the distal end of the radius, and osteoarticular loss of the MP joints of long fingers. The costal graft harvest technique is always the same. A 5-cm horizontal incision is made over the 9th rib, and the rib is exposed at the osteocartilaginous junction. Cartilaginous grafts are harvested with a scalpel, and osteocartilaginous grafts with a saw. Since 1992, 116 patients with trapezio-metacarpal arthritis have been treated by partial trapeziectomy and autologous rib cartilage grafting. One hundred patients were reviewed with an average follow-up of 5.6 years. The results were better than those of trapeziectomy with tendon interposition or ligamentous reconstruction, owing to good stability of the thumb ray height. For the treatment of radioscaphoid osteoarthritis following scaphoid non union or chronic scapholunate instability, partial carpal arthrodesis and resection of the first row are the classical techniques. As an alternative to these procedures, 18 patients were treated by resection of the proximal portion of the scaphoid and insertion of an osteochondral costal autograft. Mean follow-up is 4.1 years. The results are excellent or good in 15 cases, fair in 2 cases, and poor in 1 case (luxation of the graft). Four patients with articular malunion of the distal radius received an osteocartilaginous costal graft to reconstruct the articular surface of the radius while avoiding partial or total arthrodesis of the wrist. Four patients with segmental osteoarticular loss of the longfingers were treated with the same technique, thereby avoiding silicone arthroplasty. We review the literature on cartilaginous rib grafts in maxillofajcial and orthopaedic surgery. In our experience, MRI and biopsy show viable cartilage but also histologic changes such as revascularization, fibrous transformation and bone metaplasia. PMID:17450679

Tropet, Yves; Lepage, Daniel; Gallinet, David; Obert, Laurent; Garbuio, Patrick; Vichard, Philippe

2006-10-01

393

Switchable Adhesion from Bicomponent Polymeric Brushes  

NASA Astrophysics Data System (ADS)

We investigated the adhesive and wetting properties of bicomponent polymeric brushes made from end functionalized hydrophilic and hydrophobic polymer chains. The molecular organization of the mixed brush could be varied reversibly by exposure to selective solvents for the two polymers. Adhesive properties were tested by debonding a flat ended probe from soft pressure-sensitive-adhesives (hydrophobic & hydrophilic) and wetting properties were tested by contact angle measurements of water & diiodomethane droplets. The bicomponent brushes were chemically grafted on silicon wafers from end-functionalized chains. Wetting experiments were done directly on the wafers while for adhesion experiments, the wafers were glued on the flat end of the probe prior to the tests. In all cases the organization of the bicomponent brush could be modified reproducibly and reversibly by exposure to selective solvents. Following this strategy we succeeded to create remarkably stable adaptive polymer surfaces that can modify their adhesion and wetting reversibly and also tune them by varying the ratio of the bicomponent brush layer.

Retsos, Haris; Gorodyska, Ganna; Creton, Costantino

2005-03-01

394

Synthesis and characterization of a novel graft copolymer of partially carboxymethylated guar gum and N-vinylformamide.  

PubMed

Graft copolymer of partially carboxymethylated guar gum (CMGOH) and N-vinylformamide (NVF) was synthesized by free radical polymerization using 2,2-Azobis [2-(2-imadazolin-2-yl) propane] dihydrochloride (AIPH) as initiator. The effect of various reaction parameters such as concentration of NVF, CMGOH, sulphuric acid and AIPH, as well as reaction time and temperature were investigated, and the grafting conditions were optimized. Percent total conversion, % grafting, grafting efficiency (%) and percent add on under different conditions were evaluated and compared. The reaction mechanism for graft copolymerization discussed. Studies on swelling, metal ion uptake and flocculation properties were carried out in aqueous medium and the results obtained are presented and discussed. Both CMGOH and its corresponding graft copolymer samples were characterized by Fourier transform infrared spectroscopy and thermogravimetric analysis. Looking at the reasonable results obtained, the synthesized graft copolymers CMGOH-g-NVF, may be exploited as potential candidates for some industrial important applications as flocculent superabsorbent, and other similar applications. PMID:25439961

Mishra, Madan Mohan; Mishra, Dinesh Kumar; Mishra, Pushyamitra; Behari, Kunj

2015-01-22

395

Side-Branched AAA Stent Graft Insertion Using Navigation Technology: A Phantom Study  

Microsoft Academic Search

Objective: To evaluate the feasibility of a side-branched stent graft inserted in an artificial abdominal aortic aneurysm (AAA), using navigation technology, and to compare procedure duration and dose of radiation with control trials. Methods: A custom-made stent graft was inserted into an artificial AAA using navigation technology in combination with fluoroscopy. The navigation technology was based on three-dimensional visualization of

F. Manstad-Hulaas; S. Ommedal; G. A. Tangen; P. Aadahl; T. N. Hernes

2007-01-01

396

Enhancing antibiofouling performance of Polysulfone (PSf) membrane by photo-grafting of capsaicin derivative and acrylic acid  

NASA Astrophysics Data System (ADS)

Biofouling is a critical issue in membrane water and wastewater treatment. Herein, antibiofouling PSf membrane was prepared by UV-assisted graft polymerization of acrylic acid (AA) and a capsaicin derivative, N-(5-methyl-3-tert-butyl-2-hydroxy benzyl) acrylamide (MBHBA), on PSf membrane. AA and MBHBA were used as hydrophilic monomer and antibacterial monomer separately. The membranes were characterized by FTIR-ATR, contact angle, SEM, AFM, cross-flow filtration unit, antifouling and antibacterial measurements. Verification of MBHBA and AA that photo-chemically grafted onto the PSf membrane surface is confirmed by carbonyl stretching vibration at ?1655 cm-1 and ?1730 cm-1, separately. The increasing AA concentration accelerates the graft-polymerization of MBHBA and resulted in a more hydrophilic surface. Consequently, antifouling property of the membranes was improved on a large level. The flux recovery rate can achieve 100% during the cyclic test, which may be attributed to the more hydrophilic and smooth surface, as well as the decreased membrane pore size. Most importantly, the presence of AA in graft co-polymer does not affect the antibacterial activity of MBHBA. That may be induced by the increasing chain length and flexibility of the grafted polymer chains.

Wang, Jian; Sun, Haijing; Gao, Xueli; Gao, Congjie

2014-10-01

397

Bone graft substitute: allograft and xenograft.  

PubMed

Rapid bone graft incorporation for structural rigidity is essential. Early range of motion, exercise, and weight-bearing are keys to rehabilitation. Structural and nonstructural bone grafts add length, height, and volume to alter alignment, function, and appearance. Bone graft types include: corticocancellous autograft, allograft, xenograft, and synthetic graft. Autogenic grafts are harvested from the patient, less likely to be rejected, and more likely to be incorporated; however, harvesting adds a procedure and donor site complication is common. Allografts, xenografts, and synthetic grafts eliminate secondary procedures and donor site complications; however, rejection and slower incorporation can occur. PMID:25440415

Shibuya, Naohiro; Jupiter, Daniel C

2015-01-01

398

[Plaque surgery for Peyronie's disease: heterologous grafts].  

PubMed

Surgical treatment of Induratio Penis Plastica includes conservative procedures (phalloplasty), substitutive procedures (prosthesis) and combined procedures (phalloplasty plus prosthesis). Our policy for conservative treatment is based on radical removal of the plaque and replacement with biological patches. During a 15 year experience we employed lyophilized dura mater, autologous dermal graft, preputial skin, cadaveric dermal graft (AlloDerm), venous graft and porcine SIS (Small Intestine Submucosa) graft. Our experience confirms the superiority of venous grafts, but preliminary results with SIS grafts are encouraging. PMID:12868152

Paradiso, Matteo; Sedigh, Omid; Milan, Gian Luca

2003-06-01

399

High temperature structural, polymeric foams from high internal emulsion polymerization  

SciTech Connect

In 1982, a high internal phase emulsion (HIPE) polymerization process to manufacture microcellular, polymeric foam systems was patented by Unilever. This patent discloses a polymerization process that occurs in a water-in-oil emulsion in which the water represents at least 76% of the emulsion by volume. The oil phase consists of vinyl monomers such as styrene and acrylates that are crosslinked by divinyl monomers during polymerization. After polymerization and drying to remove the water phase, the result is a crosslinked polymer foam with an open cell microstructure that is homogeneous throughout in terms of morphology, density, and mechanical properties. Since 1982, numerous patents have examined various HIPE polymerized foam processing techniques and applications that include absorbents for body fluids, cleaning materials, and ion exchange systems. All the published HIPE polymerized foams have concentrated on materials for low temperature applications. Copolymerization of styrene with maleic anhydride and N-substituted maleimides to produce heat resistant thermoplastics has been studied extensively. These investigations have shown that styrene will free radically copolymerize with N-substituted maleimides to create an alternating thermoplastic copolymer with a Tg of approximately 200{degrees}C. However, there are many difficulties in attempting the maleimide styrene copolymerization in a HIPE such as lower polymerization temperatures, maleimide solubility difficulties in both styrene and water, and difficulty obtaining a stable HIPE with a styrene/maleimide oil phase. This work describes the preparation of copolymer foams from N-ethylmaleimide and Bis(3-ethyl-5-methyl-4-maleimide-phenyl)methane with styrene based monomers and crosslinking agents.

Hoisington, M.A.; Duke, J.R.; Apen, P.G.

1996-02-01

400

Properties of extruded starch-poly(methyl acrylate) graft copolymers prepared from spherulites formed from amylose-oleic acid inclusion complexes  

Technology Transfer Automated Retrieval System (TEKTRAN)

Mixtures of high amylose corn starch and oleic acid were processed by steam jet-cooking, and the dispersions were rapidly cooled to yield amylose-oleic acid inclusion complexes as sub-micron spherulites and spherulite aggregates. Dispersions of these spherulite particles were then graft polymerized ...

401

Plasma aminofunctionalisation of PVDF microfiltration membranes: comparison of the in plasma modifications with a grafting method using ESCA and an amino-selective fluorescent probe  

Microsoft Academic Search

Microfiltration membranes of polyvinylidenefluoride (PVDF) are promising materials for the development of functional polymeric membranes. The aim of this work is the investigation of typical plasma processes such as continuous plasma, pulse plasma and plasma graft polymerisation concerning their effect of functionalisation with primary amino groups using a mixture of nitrogen and hydrogen, ammonia, allylamine and diaminocyclohexane. The relative amounts

M Müller; C Oehr

1999-01-01

402

Integration of RAFT polymerization and click chemistry to fabricate PAMPS modified macroporous polypropylene membrane for protein fouling mitigation.  

PubMed

A copper (I)-catalyzed azide-alkyne cycloaddition (CuAAC) grafting-to method was used to tether alkyne-terminated poly(2-acrylamido-2-methyl propane sulfonic acid) (alkyne-PAMPS) to the azide functionalized macroporous polypropylene membrane (MPPM-N3). Alkyne-PAMPS was synthesized by the reversible addition-fragmentation chain transfer polymerization (RAFT) of AMPS with an alkyne-terminated trithiocarbonate served as a chain transfer agent. The combination of RAFT polymerization with click chemistry to graft polymer to the surface of polypropylene membrane produced relatively high grafting density and controllable grafting chain length. The structure and composition of the modified and unmodified MPPM surfaces were analyzed by attenuated total reflection-Fourier transform infrared spectroscopy (ATR/FT-IR), X-ray photoelectron spectroscopy (XPS); field emission scanning electron microscopy (FE-SEM) was employed to observe the morphological changes on the membrane surface. The permeation performances were tested by the filtration of protein dispersion. The experimental results show that with the grafting degree going up, the relative flux reduction decreases, while the relative flux recovery ratio increases, and the protein fouling is obviously mitigated by tethering PAMPS to the membrane surface. The modified membranes can be potentially applied for fouling reduction during the filtration of proteins. PMID:25217729

Wang, Yun; Wang, Li-Li; He, Xiao-Chun; Zhang, Zi-Jun; Yu, Hai-Yin; Gu, Jia-Shan

2014-12-01

403

Evidence for vertical phase separation in densely grafted, high-molecular-weight poly( N -isopropylacrylamide) brushes in water  

NASA Astrophysics Data System (ADS)

The detailed conformational change of poly( N -isopropylacrylamide) (PNIPAM) brushes at high grafting density in D2O was investigated as a function of temperature using neutron reflection. PNIPAM chains were grafted at high surface density from gold and silicon oxide surfaces by atom transfer radical polymerization. Whereas single layer profiles were observed for temperatures below and above the transition region, bilayer profiles were observed for a narrow range of temperatures near the transition. This nonmonotonic change in the concentration profile with temperature is discussed in the context of theoretical models of vertical phase separation within a brush.

Yim, H.; Kent, M. S.; Satija, S.; Mendez, S.; Balamurugan, S. S.; Balamurugan, S.; Lopez, G. P.

2005-11-01

404

Graft copolymerization of N-vinylformamide onto sodium carboxymethylcellulose and study of its swelling, metal ion sorption and flocculation behaviour  

Microsoft Academic Search

The present paper reports the graft copolymerization of N-vinylformamide onto sodium carboxymethylcellulose by free radical polymerization using potassium peroxymonosulphate\\/thiourea redox system in an inert atmosphere. The reaction conditions for maximum grafting have been optimized by varying the reaction variables, including the concentration of N-vinylformamide (12.0×10?2–28.0×10?2moldm?3), potassium peroxymonosulphate (4.0×10?3–12.0×10?3moldm?3), thiourea (1.2×10?3–4.4×10?3moldm?3), sulphuric acid (2.0×10?3–10.0×10?3moldm?3), sodium carboxymethylcellulose (0.2–1.8gdm?3) along with time duration

Jasaswini Tripathy; Dinesh Kumar Mishra; Kunj Behari

2009-01-01

405

Plant grafting: new mechanisms, evolutionary implications  

PubMed Central

Grafting, an old plant propagation practice, is still widely used with fruit trees and in recent decades also with vegetables. Taxonomic proximity is a general prerequisite for successful graft-take and long-term survival of the grafted, composite plant. However, the mechanisms underlying interspecific graft incompatibility are as yet insufficiently understood. Hormonal signals, auxin in particular, are believed to play an important role in the wound healing and vascular regeneration within the graft union zone. Incomplete and convoluted vascular connections impede the vital upward and downward whole plant transfer routes. Long-distance protein, mRNA and small RNA graft-transmissible signals currently emerge as novel mechanisms which regulate nutritional and developmental root/top relations and may play a pivotal role in grafting physiology. Grafting also has significant pathogenic projections. On one hand, stock to scion mechanical contact enables the spread of diseases, even without a complete graft union. But, on the other hand, grafting onto resistant rootstocks serves as a principal tool in the management of fruit tree plagues and vegetable soil-borne diseases. The ‘graft hybrid’ historic controversy has not yet been resolved. Recent evidence suggests that epigenetic modification of DNA-methylation patterns may account for certain graft-transformation phenomena. Root grafting is a wide spread natural phenomenon; both intraspecific and interspecific root grafts have been recorded. Root grafts have an evolutionary role in the survival of storm-hit forest stands as well as in the spread of devastating diseases. A more fundamental evolutionary role is hinted by recent findings that demonstrate plastid and nuclear genome transfer between distinct Nicotiana species in the graft union zone, within a tissue culture system. This has led to the formation of alloploid cells that, under laboratory conditions, gave rise to a novel, alloploid Nicotiana species, indicating that natural grafts may play a role in plant speciation, under certain circumstances. PMID:25566298

Goldschmidt, Eliezer E.

2014-01-01

406

Upper limb grafts for hemodialysis access.  

PubMed

Arteriovenous (AV) grafts are required for hemodialysis access when options for native fistulas have been fully exhausted, where they continue to play an important role in hemodialysis patients, offering a better alternative to central vein catheters. When planning autogenous accesses using Doppler ultrasound, adequate arterial inflow and venous outflow must be consciously preserved for future access creation with grafts. Efforts to improve graft patency include changing graft configuration, graft biology and hemodynamics. Industry offers early cannulation grafts to reduce central catheter use and a bioengineered graft is undergoing clinical studies. Although the outcome of AV grafts is inferior to fistulas, grafts can provide long-term hemodialysis access that is a better alternative to central venous catheters. AV grafts have significant drawbacks, mainly poor patency, infection and cost but also have some advantages: early maturation, ease of creation and needling and widespread availability. The outcome of AV graft surgery is variable from center to center. The primary patency rate for AV grafts is 58% at 6 months and the secondary patency rate is 76% at 6 months and 55% at 18 months. There are centers of excellence that report a 1 year secondary patency rate of up to 91%. In this review of the use of AV grafts for hemodialysis access in the upper extremities, technical issues involved in planning the access and performing the surgery in its different configurations are discussed and the role of surveillance and maintenance with their attendant surgical and radiological interventions is described. PMID:25751548

Shemesh, David; Goldin, Ilya; Verstandig, Anthony; Berelowitz, Daniel; Zaghal, Ibrahim; Olsha, Oded

2015-03-01

407

Surface grafting density analysis of high anti-clotting PU-Si-g-P(MPC) films  

NASA Astrophysics Data System (ADS)

Well-defined zwitterionic polymer brushes with good blood compatibility were studied, grafted from polyurethane (PU) substrate (PU-Si-g-P(MPC)) by surface-initiated reverse atom transfer radical polymerization (SI-RATRP). We found that the structure of polymer brushes and hence their properties greatly depend on the grafting density. To solve the problems of the normal method for grafting density measurement, i.e., more requirements for qualified and proficient instrument operator, we established an effective and feasible way instead of the conventional method of spectroscopic ellipsometer combined with gel permeation chromatograph (ELM/GPC) to calculate the grafting density of PU-Si-g-P(MPC) films by using a software named ImageJ 1.44e in combination with scanning electronic microscope (SEM) or atomic microscope (AFM). X-ray photoelectron spectroscopy (XPS), SEM and AFM were employed to analyze the surface topography and changes of elements before and after graft modification of the synthetic PU-Si-g-P(MPC) biofilms.

Lu, Chun-Yan; Zhou, Ning-Lin; Xiao, Ying-Hong; Tang, Yi-Da; Jin, Su-Xing; Wu, Yue; Zhang, Jun; Shen, Jian

2012-02-01

408

Endocytosis of PEGylated nanoparticles accompanied by structural and free energy changes of the grafted polyethylene glycol.  

PubMed

Nanoparticles (NPs) are in use to efficiently deliver drug molecules into diseased cells. The surfaces of NPs are usually grafted with polyethylene glycol (PEG) polymers, during so-called PEGylation, to improve water solubility, avoid aggregation, and prevent opsonization during blood circulation. The interplay between grafting density ?p and grafted PEG polymerization degree N makes cellular uptake of PEGylated NPs distinct from that of bare NPs. To understand the role played by grafted PEG polymers, we study the endocytosis of 8 nm sized PEGylated NPs with different ?p and N through large scale dissipative particle dynamics (DPD) simulations. The free energy change Fpolymer of grafted PEG polymers, before and after endocytosis, is identified to have an effect which is comparable to, or even larger than, the bending energy of the membrane during endocytosis. Based on self-consistent field theory Fpolymer is found to be dependent on both ?p and N. By incorporating Fpolymer, the critical ligand-receptor binding strength for PEGylated NPs to be internalized can be correctly predicted by a simple analytical equation. Without considering Fpolymer, it turns out impossible to predict whether the PEGylated NPs will be delivered into the diseased cells. These simulation results and theoretical analysis not only provide new insights into the endocytosis process of PEGylated NPs, but also shed light on the underlying physical mechanisms, which can be utilized for designing efficient PEGylated NP-based therapeutic carriers with improved cellular targeting and uptake. PMID:25002266

Li, Ying; Kröger, Martin; Liu, Wing Kam

2014-10-01

409

Polymerization of anionic wormlike micelles.  

PubMed

Polymerizable anionic wormlike micelles are obtained upon mixing the hydrotropic salt p-toluidine hydrochloride (PTHC) with the reactive anionic surfactant sodium 4-(8-methacryloyloxyoctyl)oxybenzene sulfonate (MOBS). Polymerization captures the cross-sectional radius of the micelles (approximately 2 nm), induces micellar growth, and leads to the formation of a stable single-phase dispersion of wormlike micellar polymers. The unpolymerized and polymerized micelles were characterized using static and dynamic laser light scattering, small-angle neutron scattering, 1H NMR, and stopped-flow light scattering. Stopped-flow light scattering was also used to measure the average lifetime of the unpolymerized wormlike micelles. A comparison of the average lifetime of unpolymerized wormlike micelles with the surfactant monomer propagation rate was used to elucidate the mechanism of polymerization. There is a significant correlation between the ratio of the average lifetime to the monomer propagation rate and the average aggregation number of the polymerized wormlike micelles. PMID:16430253

Zhu, Zhiyuan; González, Yamaira I; Xu, Hangxun; Kaler, Eric W; Liu, Shiyong

2006-01-31

410

Synthesis of amphipathic block copolymers based on polyisobutylene and polyoxyethylene and their application in emulsion polymerization  

SciTech Connect

Polymer colloids stabilized by polymeric surfactants are of great interest both commercially and academically. It has been found that these materials enhance latex stabilization in a number of applications. The polymeric surfactants are amphipathic block and graft copolymers containing both hydrophilic and hydrophobic moieties. The current study involved the synthesis of a series of amphipathic triblock copolymers, polyisobutylene-block-polyoxyethylene-block-polyisobutylene (PIB-b-POE-b-PIB), for use in the emulsion polymerization of styrene (STY), methyl methacrylate (MMA), and vinyl acetate (VAc). The stabilizing effectiveness of these triblock copolymers was studied as a function of their blocklength. When the molecular weight of the POE center block was changed from M{sub n} = 2,000 to 20,000 g/mole, stable lattices were obtained in emulsion polymerization with MMA, STY, and VAc as the monomers. In all cases, the polymerization rates remained constant, while the number of particles/volume decreased with increasing POE chain length. When the molecular weight of the PIB end blocks was changed from M{sub n} = 400 to 2,600 g/mole keeping the molecular weight of the POE center block constant at M{sub n} = 20,000 g/mole, the poly(methyl methacrylate) and poly(vinyl acetate) lattices exhibited similar behavior, i.e., the number of particles and particle sizes remained the same, but the rate of polymerization reached a maximum at 87 wt% POE content. In the case of poly(styrene) both the rate of polymerization and the number of particles remained constant. The emulsion polymerization of other monomers such as butadiene, acrylonitrile, methyl acrylate, ethyl acrylate, and butyl acrylate was carried out by using one triblock copolymer, i.e., PIB(400)-b-POE (8,000)-b-PIB-(400). Stable lattices were also formed in all cases.

Sar, B.

1992-12-31

411

Polymeric waveguides for optical backplanes  

Microsoft Academic Search

Organic polymeric materials offer great promise for the creation of optical guided-wave structures. We have developed a number of new polymeric compositions which can be used to fabricate optical waveguide circuitry characterized by low loss and high thermal stability (up to 75 years at 120 degree(s)C for 840 nm wavelength). This technology makes possible the fabrication of complex point-to-point optical

Lawrence W. Shacklette; K. M. Stengel; L. Eldada; C. Xu; James T. Yardley

1995-01-01

412

POST CORONARY ARTERY BYPASS GRAFT STUDY (CABG)  

EPA Science Inventory

Relative effectiveness of moderate versus more aggressive lipid lowering, and of low dose anticoagulation versus placebo, in delaying saphenous vein coronary bypass graft atherosclerosis and preventing occlusion of saphenous grafts of patients with saphenous vein coronary bypass ...

413

Types of Coronary Artery Bypass Grafting  

MedlinePLUS

... best option for you based on your needs. Traditional Coronary Artery Bypass Grafting Traditional CABG is used when at least one major ... Grafting This type of CABG is similar to traditional CABG because the chest bone is opened to ...

414

Composite Arterial Y Graft Has Less Coronary Flow Reserve Than Independent Grafts  

Microsoft Academic Search

Background. It is not known whether a composite Y graft of the left internal thoracic artery can provide sufficient blood flow to the whole left coronary system. The aim of this study was to compare regional myocar- dial blood flow (MBF) and coronary flow reserve after coronary artery bypass grafting using arterial composite Y graft or independent arterial grafts. Methods.

Genichi Sakaguchi; Eiji Tadamura; Motoaki Ohnaka; Keiichi Tambara; Kazunobu Nishimura; Masashi Komeda

2010-01-01

415

Composite arterial Y graft has less coronary flow reserve than independent grafts  

Microsoft Academic Search

Background. It is not known whether a composite Y graft of the left internal thoracic artery can provide sufficient blood flow to the whole left coronary system. The aim of this study was to compare regional myocardial blood flow (MBF) and coronary flow reserve after coronary artery bypass grafting using arterial composite Y graft or independent arterial grafts.Methods. Positron emission

Genichi Sakaguchi; Eiji Tadamura; Motoaki Ohnaka; Keiichi Tambara; Kazunobu Nishimura; Masashi Komeda

2002-01-01

416

Recanalization of an Occluded Infrainguinal Vein Graft Complicated by Graft Aneurysm  

SciTech Connect

The technique of subintimal angioplasty has been described for the recanalisation of native vessels after occlusion of infrainguinal vascular bypass grafts. We report a case in which an attempt at such treatment resulted in inadvertent but successful recanalisation of the occluded vein graft instead. This was complicated by graft perforation and subsequent graft aneurysm which was successfully treated with a covered stent.

Kakani, Nirmal; Travis, Simon; Hancock, John [Royal Cornwall Hospital, Department of Clinical Imaging (United Kingdom)], E-mail: John.Hancock@rcht.cornwall.nhs.uk

2007-11-15

417

Direct polymerization of proteins.  

PubMed

We report the synthesis of active polymers of superfolder green fluorescent protein (sfGFP) in one step using Click chemistry. Up to six copies of the non-natural amino acids (nnAAs) p-azido-l-phenylalanine (pAzF) or p-propargyloxy-l-phenylalanine (pPaF) were site-specifically inserted into sfGFP by cell-free protein synthesis (CFPS). sfGFP containing two or three copies of these nnAAs were coupled by copper-catalyzed azide-alkyne cycloaddition to synthesize linear or branched protein polymers, respectively. The protein polymers retained ?63% of their specific activity (i.e., fluorescence) after coupling. Polymerization of a concentrated solution of triply substituted sfGFP resulted in fluorescent macromolecular particles. Our method can be generalized to synthesize polymers of a protein or copolymers of any two or more proteins, and the conjugation sites can be determined exactly by standard genetic manipulation. Polymers of proteins and small molecules can also be created with this technology to make a new class of scaffolds or biomaterials. PMID:24200191

Albayrak, Cem; Swartz, James R

2014-06-20

418

Kinetics of silica polymerization  

SciTech Connect

The polymerization of silicic acid in geothermal brine-like aqueous solutions to produce amorphous silica in colloidal form has been studied experimentally and theoretically. A large amount of high quality experimental data has been generated over the temperature rang 23 to 100{sup 0}C. Wide ranges of dissolved silica concentration, pH, and sodium chloride concentration were covered. The catalytic effects of fluoride and the reaction inhibiting effects of aluminum and boron were studied also. Two basic processes have been separately studied: the formation of new colloidal particles by the homogeneous nucleation process and the deposition of dissolved silica on pre-existing colloidal particles. A rigorous theory of the formation of colloidal particles of amorphous silica by homogeneous nucleation was developed. This theory employs the Lothe-Pound formalism, and is embodied in the computer code SILNUC which quantitatively models the homogeneous nucleation and growth of colloidal silica particles in more than enough detail for practical application. The theory and code were extensively used in planning the experimental work and analyzing the data produced. The code is now complete and running in its final form. It is capable of reproducing most of the experimental results to within experimental error. It is also capable of extrapolation to experimentally inaccessible conditions, i.e., high temperatures, rapidly varying temperature and pH, etc.

Weres, O.; Yee, A.; Tsao, L.

1980-05-01

419

Synthesis of Externally Initiated Poly(3-alkylthiophene)s via Kumada Catalyst Transfer Polymerization  

NASA Astrophysics Data System (ADS)

The ability of chemists to design and synthesize pi conjugated organic polymers with precise control over their physical and electronic properties remains the key to technological breakthroughs using polymeric material in electronic and photonic devices. Kumada catalyst transfer polymerization (KCTP) technique and Grignard metathesis (GRIM) method have enabled the synthesis of highly regioregular polymers with controlled molecular weights, narrow polydispersity index and uniform end groups. Applying this technique toward external initiation of polymers would enable the preparation of sophisticated and beneficial polymer architectures such as surface grafted polymers. This work presents an investigation of various mechanistic parameters for external initiation of poly(3-alkylthiophene). The effects of binding ligand variation on the Nickel catalyst were investigated utilizing a novel methodology allowing facile screening of ligands. Poly(3-hexylthiophene) was synthesized with high percentage initiator headgroup incorporation with triphenylphosphine ligand while the use of bidentate ligands such as diphenylphosphinopropane only resulted in quantitative initiation when ligand exchange followed initiation with the more active species. A variety of functionally substituted aryl and thiophene halides were explored for their potential to act as external small molecule initiators and the reaction intermediates were characterized via spectroscopic techniques as well as theoretical calculations. Aryl halides were found to be more stable than thiophene halides and the type and position of the initiator functionality has played a deciding role in the polymerization mechanism. Ortho substitution stabilized the aryl-Ni intermediate complex via favorable orbital overlap and kinetic effects as a result of steric hindrance were demonstrated to affect the success of the external initiation. Surface-grafted poly(3-methylthiophene) thin films were synthesized from indium tin oxide where polymer thin film thicknesses were regulated by the variation of monomer solution and polymerization time. Photoelectron spectroscopy analysis had demonstrated that electrochemical oxidation of surface grafted thin films affords the ability to tune the work function and ionization potential. Such materials with controllable thicknesses and electronic properties have the potential to be useful as components in organic photovoltaic devices.

D'Avanzo, Antonella

420

Time-resolved X-ray scattering study of actin polymerization from profilactin.  

PubMed

The polymerization of actin in solutions of purified calf spleen actin or profilactin (1-10 mg . ml-1) was followed by synchrotron radiation X-ray solution scattering. At the concentration used, polymerization of actin from profilactin or actin occurs without any lag phase. It is shown by a combination of solution scattering, model calculations and electron microscopy that contrary to the conclusions from previous viscometry studies, filaments form without any lag phase in profilactin solution but aggregate in bundles or networks. This phenomenon is independent of the method used to induce polymerization: slow temperature increase, temperature jump in the presence of polymerizing salts or fast mixing with salt. This aggregation explains the lower final viscosity levels, as compared to actin solutions, observed during the polymerization of actin from profilactin. PMID:4085417

Sayers, Z; Koch, M H; Bordas, J; Lindberg, U

1985-01-01

421

Skin flaps and grafts - self-care  

MedlinePLUS

A skin graft is a piece of healthy skin removed from one area of your body to repair damaged or ... Autograft - self-care; Skin transplant - self-care; Split-skin graft - self-care; Full thickness skin graft - self-care; ...

422

A Model of Vein Graft Intimal Hyperplasia  

Microsoft Academic Search

When vein graft is implanted in the arterial system, the vein graft wall becomes thicker as an adaptive process. We have developed a model of early adaptive vein graft intimal thickening induced by shear stress. Intimal thickness and the rate of intimal thickening are expressed as functions of shear stress and time based on experimental data. The model describes the

Roger Tran-Son-Tay; Minki Hwang; Scott A. Berceli; C. Keith Ozaki; Marc Garbey

2007-01-01

423

Construction of a bioengineered cardiac graft  

Microsoft Academic Search

Objectives: Currently available graft materials for repair of congenital heart defects cause significant morbidity and mortality because of their lack of growth potential. An autologous cell-seeded graft may improve patient outcomes. We report our initial experience with the construction of a biodegradable graft seeded with cultured rat or human cells and identify their 3-dimensional growth characteristics. Methods: Fetal rat ventricular

Ren-Ke Li; Terrence M. Yau; Richard D. Weisel; Donald A. G. Mickle; Tetsuro Sakai; Angel Choi; Zhi-Qiang Jia

2000-01-01

424

Functional Grafts of the Anterior Pituitary Gland  

Microsoft Academic Search

A study has been made of pituitary grafts placed into hypophysectomized adult rats under the median eminence of the tuber cinereum, under the temporal lobe of the brain and into the hypophysial capsule. Good union was obtained in all three sites, the grafts becoming richly vascularized and remaining viable for long periods. Grafts placed under the median eminence acquired vascular

G. W. Harris; Dora Jacobsohn

1952-01-01

425

Self-assembled polymeric micelles based on hyaluronic acid-g-poly(D,L-lactide-co-glycolide) copolymer for tumor targeting.  

PubMed

Graft copolymer composed hyaluronic acid (HA) and poly(D,L-lactide-co-glycolide) (PLGA) (HAgLG) was synthesized for antitumor targeting via CD44 receptor of tumor cells. The carboxylic end of PLGA was conjugated with hexamethylenediamine (HMDA) to have amine end group in the end of chain (PLGA-amine). PLGA-amine was coupled with carboxylic acid of HA. Self-assembled polymeric micelles of HAgLG have spherical morphologies and their sizes were around 50-200 nm. Doxorubicin (DOX)-incorporated polymeric micelles were prepared by dialysis procedure. DOX was released over 4 days and its release rate was accelerated by the tumoric enzyme hyaluronidase. To assess targetability of polymeric micelles, CD44-positive HepG2 cells were employed treated with fluorescein isothiocyanate (FITC)-labeled polymeric micelles. HepG2 cells strongly expressed green fluorescence at the cell membrane and cytosol. However, internalization of polymeric micelles were significantly decreased when free HA was pretreated to block the CD44 receptor. Furthermore, the CD44-specific anticancer activity of HAgLG polymeric micelles was confirmed using CD44-negative CT26 cells and CD44-positive HepG2 cells. These results indicated that polymeric micelles of HaLG polymeric micelles have targetability against CD44 receptor of tumor cells. We suggest HAgLG polymeric micelles as a promising candidate for specific drug targeting. PMID:25216338

Son, Gyung Mo; Kim, Hyun Yul; Ryu, Je Ho; Chu, Chong Woo; Kang, Dae Hwan; Park, Su Bum; Jeong, Young-Il

2014-01-01

426

Self-Assembled Polymeric Micelles Based on Hyaluronic Acid-g-Poly(d,l-lactide-co-glycolide) Copolymer for Tumor Targeting  

PubMed Central

Graft copolymer composed hyaluronic acid (HA) and poly(d,l-lactide-co-glycolide) (PLGA) (HAgLG) was synthesized for antitumor targeting via CD44 receptor of tumor cells. The carboxylic end of PLGA was conjugated with hexamethylenediamine (HMDA) to have amine end group in the end of chain (PLGA-amine). PLGA-amine was coupled with carboxylic acid of HA. Self-assembled polymeric micelles of HAgLG have spherical morphologies and their sizes were around 50–200 nm. Doxorubicin (DOX)-incorporated polymeric micelles were prepared by dialysis procedure. DOX was released over 4 days and its release rate was accelerated by the tumoric enzyme hyaluronidase. To assess targetability of polymeric micelles, CD44-positive HepG2 cells were employed treated with fluorescein isothiocyanate (FITC)-labeled polymeric micelles. HepG2 cells strongly expressed green fluorescence at the cell membrane and cytosol. However, internalization of polymeric micelles were significantly decreased when free HA was pretreated to block the CD44 receptor. Furthermore, the CD44-specific anticancer activity of HAgLG polymeric micelles was confirmed using CD44-negative CT26 cells and CD44-positive HepG2 cells. These results indicated that polymeric micelles of HaLG polymeric micelles have targetability against CD44 receptor of tumor cells. We suggest HAgLG polymeric micelles as a promising candidate for specific drug targeting. PMID:25216338

Son, Gyung Mo; Kim, Hyun Yul; Ryu, Je Ho; Chu, Chong Woo; Kang, Dae Hwan; Park, Su Bum; Jeong, Young-IL

2014-01-01

427

Plasma-mediated grafting of poly(ethylene glycol) on polyamide and polyester surfaces and evaluation of antifouling ability of modified substrates.  

PubMed

A simple cold plasma technique was developed to functionalize the surfaces of polyamide (PA) and polyester (PET) for the grafting of polyethylene glycol (PEG) with the aim of reducing biofilm formation. The surfaces of PA and PET were treated with silicon tetrachloride (SiCl4) plasma, and PEG was grafted onto plasma-functionalized substrates (PA-PEG, PET-PEG). Different molecular weights of PEG and grafting times were tested to obtain optimal surface coverage by PEG as monitored by electron spectroscopy for chemical analysis (ESCA). The presence of a predominant C-O peak on the PEG-modified substrates indicated that the grafting was successful. Data from hydroxyl group derivatization and water contact angle measurement also indicated the presence of PEG after grafting. The PEG-grafted PA and PET under optimal conditions had similar chemical composition and hydrophilicity; however, different morphology changes were observed after grafting. Both PA-PEG and PET-PEG surfaces developed under optimal plasma conditions showed about 96% reduction in biofilm formation by Listeria monocytogenes compared with that of the corresponding unmodified substrates. This plasma functionalization method provided an efficient way to graft PEG onto PA and PET surfaces. Because of the high reactivity of Si-Cl species, this method could potentially be applied to other polymeric materials. PMID:17500575

Dong, Baiyan; Jiang, Hongquan; Manolache, Sorin; Wong, Amy C Lee; Denes, Ferencz S

2007-06-19

428

Polymeric materials for neovascularization  

NASA Astrophysics Data System (ADS)

Revascularization therapies have emerged as a promising strategy to treat various acute and chronic wounds, cardiovascular diseases, and tissue defects. It is common to either administer proangiogenic growth factors, such as vascular endothelial growth factor (VEGF), or transplant cells that endogenously express multiple proangiogenic factors. Additionally, these strategies utilize a wide variety of polymeric systems, including hydrogels and biodegradable plastics, to deliver proangiogenic factors in a sophisticated manner to maintain a sustained proangiogenic environment. Despite some impressive results in rebuilding vascular networks, it is still a challenging task to engineer mature and functional neovessels in target tissues, because of the increasing complexities involved with neovascularization applications. To resolve these challenges, this work aims to design a wide variety of proangiogenic biomaterial systems with tunable properties used for neovascularization therapies. This thesis describes the design of several biomaterial systems used for the delivery of proangiogenic factors in neovascularization therapies, including: an electrospun/electrosprayed biodegradable plastic patch used for directional blood vessel growth (Chapter 2), an alginate-g-pyrrole hydrogel system that biochemically stimulates cellular endogenous proangiogenic factor expression (Chapter 3), an enzyme-catalyzed alginate-g-pyrrole hydrogel system for VEGF delivery (Chapter 4), an enzyme-activated alginate-g-pyrrole hydrogel system with systematically controllable electrical and mechanical properties (Chapter 5), and an alginate-g-pyrrole hydrogel that enables the decoupled control of electrical conductivity and mechanical rigidity and is use to electrically stimulate cellular endogenous proangiogenic factor expression (Chapter 6). Overall, the biomaterial systems developed in this thesis will be broadly useful for improving the quality of a wide array of molecular and cellular based revascularization therapies.

DeVolder, Ross John

429

Tailoring surface structure of polymer nanospheres in Pickering emulsion polymerization.  

PubMed

A series of surface-functionalized polystyrene (PS) nanospheres with similar particles size of about 100 nm and adjusted content of sulfonate groups on the surface are prepared by Pickering emulsion polymerization using titania nanoparticles modified with a mixture of two surfactants as stabilizers. TEM and FE-SEM images indicate that the titania nanoparticles are firmly adsorbed on the surface of polymer nanospheres because of the electric attraction between negative charged surfactant molecules and positive charged titania particles. XPS and electrophoresis measurements confirm that the surfactant with a double bond has been successfully grafted on the surface of PS nanospheres, and the surfactant without a double bond is removed with titania nanoparticles. Polymer nanospheres with appropriate concentration of sulfonate groups on the surface have good colloidal stability in the nonpolar solvent and may be suitable for bistable electrophoretic display application. PMID:23622687

Chen, Zhi; Qin, Zhenwen; Wang, Haitao; Du, Qiangguo

2013-07-01

430

Polyether-polyester graft copolymer  

NASA Technical Reports Server (NTRS)

Described is a polyether graft polymer having improved solvent resistance and crystalline thermally reversible crosslinks. The copolymer is prepared by a novel process of anionic copolymerization. These polymers exhibit good solvent resistance and are well suited for aircraft parts. Previous aromatic polyethers, also known as polyphenylene oxides, have certain deficiencies which detract from their usefulness. These commercial polymers are often soluble in common solvents including the halocarbon and aromatic hydrocarbon types of paint thinners and removers. This limitation prevents the use of these polyethers in structural articles requiring frequent painting. In addition, the most popular commercially available polyether is a very high melting plastic. This makes it considerably more difficult to fabricate finished parts from this material. These problems are solved by providing an aromatic polyether graft copolymer with improved solvent resistance and crystalline thermally reversible crosslinks. The graft copolymer is formed by converting the carboxyl groups of a carboxylated polyphenylene oxide polymer to ionic carbonyl groups in a suitable solvent, reacting pivalolactone with the dissolved polymer, and adding acid to the solution to produce the graft copolymer.

Bell, Vernon L. (inventor)

1987-01-01

431

Grafting Strategy to Develop Single Site Titanium on an Amorphous Silica Surface  

SciTech Connect

Titanium/silica systems were prepared by grafting a titanium alkoxide (titanium isopropoxide and titanium (triethanolaminate) isopropoxide) precursor onto amorphous silica. The grafting process, which consisted of the hydrolysis of the Ti precursor by the hydroxyl groups on the silica surface, yielded samples containing Ti-loadings of 1-1.6 wt %. The as synthesized and calcined TiO2-SiO2 samples were characterized by UV-vis, FTIR, XPS, and XANES spectroscopic techniques. These systems were tested in the liquid-phase epoxidation of oct-1-ene with hydrogen peroxide reaction. Spectroscopic data indicated that titanium anchoring takes place by reaction between the alkoxide precursor and surface OH groups of the silica substrate. The nature of surface titanium species generated by chemical grafting depends largely on the titanium precursor employed. Thus, the titanium isopropoxide precursor yields tetrahedrally coordinated polymeric titanium species, which give rise to a low-efficiency catalyst. However, if an atrane precursor (titanium (triethanolaminate) isopropoxide) is employed, isolated titanium species are obtained. The fact that these species remain isolated even after calcination is due to the protective effect of the triethanolaminate ligand that avoids titanium polymerization. These differences in the titanium environment have a pivotal role in the performance of these systems in the epoxidation of alkenes with hydrogen peroxide.

Capel-Sanchez, M.; Blanco-Brieva, G; Campos-Martin, J; de Frutos, M; Wen, W; Rodriguez, J; Fierro, J

2009-01-01

432

Hydrolyzed polyacrylamide grafted carboxymethylxyloglucan based microbeads for pH responsive drug delivery.  

PubMed

The present study investigates the pharmaceutical application of hydrolyzed polyacrylamide grafted carboxymethylxyloglucan (HPam-g-CMXG), as promising polymeric material for the development of pH responsive microbeads. The graft copolymer was synthesized by conventional free radical polymerization method and saponified to enhance its functionality and characterized. An acute oral toxicity study ensured the bio-safety of developed copolymer for clinical application. Various batches of pH responsive spherical microbeads were developed and evaluated for the effect of process parameters on their overall performance. Result of in vitro drug release study (USP Type-II, paddle method) carried out in two different pH media (pH 1.2 and pH 7.4) showed a triphasic drug release pattern in all the formulations. Both the drug release and swelling of microbeads were significantly higher in simulated intestinal (alkaline) pH compared to simulated gastric (acidic) pH and this nature is desirable for targeted drug delivery. A strong correlation was observed between the process parameters and matrix composition and it directly influenced the drug transport mechanism. In conclusion, the hydrolyzed polyacrylamide grafted carboxymethylxyloglucan holds an immense potential to be explored pharmaceutically as new matrix material for the design of targeted drug delivery system. PMID:24632345

Setty, C Mallikarjuna; Deshmukh, Anand S; Badiger, Aravind M

2014-06-01

433

Silver nanoparticle based antibacterial methacrylate hydrogels potential for bone graft applications.  

PubMed

Infections are frequent and very undesired occurrences after orthopedic procedures; furthermore, the growing concern caused by the rise in antibiotic resistance is progressively dwindling the efficacy of such drugs. Artificial bone graft materials could solve some of the problems associated with the gold standard use of natural bone graft such as limited bone material, pain at the donor site and rejections if donor tissue is used. We have previously described new acrylate base nanocomposite hydrogels as bone graft materials. In the present paper, we describe the integration of silver nanoparticles in the polymeric mineralized biomaterial to provide non-antibiotic antibacterial activity against Staphylococcus epidermidis and Methicillin-resistant Staphylococcus aureus. Two different crosslinking degrees were tested and the silver nanoparticles were integrated into the composite matrix by means of three different methods: entrapment in the polymeric hydrogel before the mineralization; diffusion during the process of calcium phosphate crystallization and adsorption post-mineralization. The latter being generally the most effective method of encapsulation; however, the adsorption of silver nanoparticles inside the pores of the biomaterial led to a decreasing antibacterial activity for adsorption time longer than 2days. PMID:25746278

González-Sánchez, M Isabel; Perni, Stefano; Tommasi, Giacomo; Morris, Nathanael Glyn; Hawkins, Karl; López-Cabarcos, Enrique; Prokopovich, Polina

2015-05-01

434

Facile preparation route for nanostructured composites: surface-initiated ring-opening polymerization of ?-caprolactone from high-surface-area nanopaper.  

PubMed

In this work, highly porous nanopaper, i.e., sheets of papers made from non-aggregated nanofibrillated cellulose (NFC), have been surface-grafted with poly(?-caprolactone) (PCL) by surface-initiated ring-opening polymerization (SI-ROP). The nanopaper has exceptionally high surface area (?300 m(2)/g). The "grafting from" of the nanopapers was compared to "grafting from" of cellulose in the form of filter paper, and in both cases either titanium n-butoxide (Ti(On-Bu)4) or tin octoate (Sn(Oct)2) was utilized as a catalyst. It was found that a high surface area leads to significantly higher amount of grafted PCL in the substrates when Sn(Oct)2 was utilized as a catalyst. Up to 79 wt % PCL was successfully grafted onto the nanopapers as compared to filter paper where only 2-3 wt % PCL was grafted. However, utilizing Ti(On-Bu)4 this effect was not seen and the grafted amount was essentially similar, irrespectively of surface area. The mechanical properties of the grafted nanopaper proved to be superior to those of pure PCL films, especially at elevated temperatures. The present bottom-up preparation route of NFC-based composites allows high NFC content and provides excellent nanostructural control. This is an important advantage compared with some existing preparation routes where dispersion of the filler in the matrix is challenging. PMID:22646162

Boujemaoui, Assya; Carlsson, Linn; Malmström, Eva; Lahcini, Mohammed; Berglund, Lars; Sehaqui, Houssine; Carlmark, Anna

2012-06-27

435

Effects of irradiation on grafted skin  

SciTech Connect

The reaction of grafted skin to irradiation was studied in the rat and the optimum time for irradiation postoperatively was determined. There was a close correlation between the radiosensitivity and the vascularity of the graft and its recipient bed. Grafts showed different reactions depending on the time of irradiation after grafting. Those in the early hypovascular stage showed reactions similar to those of normal control skin. Severe reactions were observed in the hypervascular stage. Grafts in the late hypovascular stage showed more moderate reactions.

Sumi, Y.; Ueda, M.; Kaneda, T.; Eto, K.

1983-09-01

436

Preparation and characterization of composite resin by vinyl chloride grafted onto poly(BA-EHA)\\/poly(MMA-St)  

Microsoft Academic Search

Crosslinked poly(butyl acrylate-co-2-ethylhexyl acrylate)\\/poly(methyl methacrylate-co-styrene) (ACR I) latex was synthesized by multi-stage emulsion polymerization. A series of grafting vinyl chloride (VC) composite latices were prepared by emulsion copolymerization in the presence of core-shell ACR I latex. The effects of ACR I amount and its core\\/shell ratio on particle diameters of the composite latices and mechanical properties of the prepared materials

Mingwang Pan; Liucheng Zhang; Linzhan Wan; Ruiqiang Guo

2003-01-01

437

Radially and Axially Graded Multizonal Bone Graft Substitutes Targeting Critical-Sized Bone Defects from Polycaprolactone/Hydroxyapatite/Tricalcium Phosphate  

PubMed Central

Repair and regeneration of critical sized defects via the utilization of polymeric bone graft substitutes are challenges. Here, we introduce radially and axially graded multizonal bone graft substitutes fabricated from polycaprolactone (PCL), and PCL biocomposites with osteoconductive particles, that is, hydroxyapatite (HA), and ?-tricalcium phosphate (TCP). The novel bone graft substitutes should provide a greater degree of freedom to the orthopedic surgeon especially for repair of critically sized bone defects. The modulus of the graft substitute could be tailored in the axial direction upon the systematic variation of the HA/TCP concentration, while in the radial direction the bone graft substitute consisted of an outer layer with high stiffness, encapsulating a softer core with greater porosity. The biocompatibility of the bone graft substitutes was investigated using in vitro culturing of human bone marrow-derived stromal cells followed by the analysis of cell proliferation and differentiation rates. The characterization of the tissue constructs included the enzymatic alkaline phosphates (ALP) activity, microcomputed tomography imaging, and polymerase chain reaction analysis involving the expressions of bone markers, that is, Runx2, ALP, collagen type I, osteopontin, and osteocalcin, overall demonstrating the differentiation of bone marrow derived stem cells (BMSCs) via osteogenic lineage and formation of mineralized bone tissue. PMID:22764839

Ergun, Asli; Yu, Xiaojun; Valdevit, Antonio; Ritter, Arthur

2012-01-01

438

Multifunctional network-structured film coating for woven and knitted polyethylene terephthalate against cardiovascular graft-associated infections.  

PubMed

Multifunctional network-structured polymeric coat for woven and knitted forms of crimped polyethylene terephthalate PET graft was developed to limit graft-associated infections. A newly synthesized antibacterial sulfadimethoxine polyhexylene adipate-b-methoxy polyethylene oxide (SD-PHA-b-MPEO) di-block copolymer was employed. Our figures of merit revealed that the formed coat showed a porous topographic architecture which manifested paramount properties, mostly bacterial anti-adhesion efficiency and biocompatibility with host cells. Compared to untreated grafts, the coat presented marked reduction of adhered Gram-positive Staphylococcus epidermidis previously isolated from a patient's vein catheter by 2.6 and 2.3 folds for woven and knitted grafts, respectively. Similarly, bacterial anti-adhesion effect was observed for Staphylococcus aureus by 2.3 and 2.4 folds, and by 2.9 and 2.7 folds for Gram-negative Escherichia coli for woven and knitted grafts, respectively. Additionally, adhesion and growth characteristics of L929 cells on the modified grafts revealed no significant effect on the biocompatibility. In conclusion, coating of PET with (SD-PHA-b-MPEO) is a versatile approach offers the desired bacterial anti-adhesion effect and host biocompatibility. PMID:25796119

Al Meslmani, Bassam M; Mahmoud, Gihan F; Sommer, Frank O; Lohoff, Michael D; Bakowsky, Udo

2015-05-15

439

Antifungal activity, biofilm-controlling effect, and biocompatibility of poly(N-vinyl-2-pyrrolidinone)-grafted denture materials  

PubMed Central

Colonization and biofilm-formation of Candida species on denture surfaces cause Candida-associated denture stomatitis (CADS), a common, recurring disease affecting up to 67% of denture wearers. We developed poly(N-vinyl-2-pyrrolidinone)-grafted denture materials that can be repeatedly recharged with various antifungal drugs to achieve long-term antifungal and biofilm-controlling effects. The monomer, N-vinyl-2-pyrrolidinone (NVP), was grafted onto poly(methyl methacrylate) denture resins through plasma-initiated grafting polymerization. The physical properties and biocompatibility of the resulting resins were not negatively affected by the presence of up to 7.92% of grafted poly (N-vinyl-2-pyrrolidinone) (PNVP). Miconazole and chlorhexidine digluconate (CD) were used as model antifungal drugs. PNVP grafting significantly increased the drug absorption capability of the resulting denture materials. Further, the new materials showed sustained drug release and provided antifungal effects for weeks (in the case of CD) to months (in the case of miconazole). The drug-depleted resins could be recharged with the same or a different class of antifungal drug to further extend antifungal duration. If needed, drugs on the PNVP-grafted denture materials could be “washed out” (quenched) by treating with PNVP aqueous solutions to stop drug release. These results point to great potentials of the new materials in controlling biofilm-formation in a wide range of device-related applications. PMID:23708753

Sun, Xinbo; Cao, Zhengbing; Yeh, Chih-Ko; Sun, Yuyu

2013-01-01

440

Amputation of congo red dye from waste water using microwave induced grafted Luffa cylindrica cellulosic fiber.  

PubMed

The present study deals with the surface modification of Luffa cylindrica fiber through graft copolymerization of methyl acrylate/acrylamide (MA/AAm) via microwave radiation without the use of initiator. Various reaction parameters effecting grafting yield were optimized and physico-chemical properties were evaluated. The grafted Luffa cylindrica fiber showed morphological transformations, thermal stability and chemical resistance. The adsorption potential of modified fiber was investigated using adsorption isotherms for hazardous congo red dye removal from aqueous system. The maximum adsorption capacity of dye onto grafted Luffa cylindrica fiber was found to be 17.39 mg/g with best fit for Langmuir adsorption isotherm. The values of thermodynamic parameters such as enthalpy change, ?H(0) (21.27 kJ/mol), entropy change, ?S(0) (64.71 J/mol K) and free energy change, ?G(0) (-139.52 kJ/mol) were also calculated. Adsorption process was found spontaneous and endothermic in nature. PMID:25037387

Gupta, Vinod Kumar; Pathania, Deepak; Agarwal, Shilpi; Sharma, Shikha

2014-10-13